There's a long story I have to cover first. We have a player in our game who plays as a barbarian by the name of Dave (cheeky, I know.) He is the archetype of "I charge ahead" meme-based barbarian play. His character was originally chaotic evil compared to our party's collective neutral/good aligned PC's, and thus he quickly became a problem. Eventually, the DM made him change to chaotic neutral to justify being allies to us. However, he never stopped forcing us into fights we didn't want. It was never such a problem, we (our characters) got irritated and enjoyed the game regardless. But recently he's been getting crazier.

Recently, his decision was to willfully endanger the lives an integral NPC and our PC Sorcerer with threat of certain death for all three of them, because "character decisions" and luck alone saved him, along with DM implemented plot armor (which he later apologized to the rest of us for doing.) The DM heeded our concerns of "Dave's" behavior recently and how it would make perfect sense for our characters to elect to kill him now. We ultimately decided that if he were to act out again, we're pulling the trigger and killing him.

So my question is, how should we kill him? This is a homebrew campaign that caps at level 40 (for a 20/20 multiclass capability as well as a ton of rebalancing for the sake of that new level cap.) We just hit 20. He's a level 20 Barbarian, with well over 200 HP, so he is no easy target. There's the option of 4v1, but it risks our lives. If there were a smooth way to just say  "for the watch" and end him in the blink of an eye, it would be much better. Any ideas?

The question is, if the player in question wants to get rid of his character as well. There are options like the party disbanding him, because ‚they can‘t work together with evil guys‘, some party member hiring an assassins guild, or setting up some rumors in town which will make the local authorities worry about troublemakers (and let them arrest him). To be fair it seems the player seems to play his character as intended, however it might not be the best match and the question would be why this adventurer is traveling together with this party for such a long time already. Shouldn‘t he recognize them being good friends already and try to control himself (or others knowing him, putting him to sleep to save him from trouble)?

If the player just wants to bring trouble to other gamers, it might be a different topic, though. Talk open about everyone‘s feelings/enjoyment and either arrange or let the DM decide on how to proceed IMHO.

I’m playing in a group where a player is playing a character similar to Dave the Barbarian, only he’s a Rogue. We just hit 5th level and my Wizard has saved his life a few times by being creative with how I’m using my spells. 

As we hit 4th level my Wizard decided that he’s not going to go out of his way to save the Rogue’s life or protect him any more. Sure, I’ll cast Feather Fall on him if he falls, but I won’t do any outside of the box thinking to protect him and I’m going to let him die when he’s overly reckless, especially if he endangers the rest of the party in the process.

You don’t have to kill him. Just stop being super aggressive about keeping him alive. He’ll bite off more than he can chew on his own and get himself killed. Just make sure that your characters tell him every time he does something reckless and stupid that they don’t like to be more careful so that he has an opportunity to change and not put himself in a situation where he ends up dying. 

The main reason killing him has become an option is because his decisions have been at the detriment of others. He literally dragged our NPC and our sorcerer into a deadly situation because she had to hold onto him in order not to fall to her death (he was tasked with carrying the two to safety via the fly spell our wizard cast on them.) Rather than fly to safety, he ran headfirst into an enemy boss lair and nearly suffocated them. He didnt care because he doesnt need to breathe.

It's 100% a matter of a player being a troublemaker behind the guise of "character choices" and he has gotten away with it for long enough. We plan on telling him there will be consequences if he doesn't start to consider the enjoyment of others, but we won't say anything beyond that. This post is moreso just asking for ideas to kill him IF we end up having to, though I hope we don't.

If all of you feel the player is being a troublemaker, I wonder why the DM is not intercepting, e.g. freeze him in mid-air, teleport him away, suddenly stuck him with a disease like being blind (during combat), simply not letting him play the way he wants? If the DM is afraid of telling him, maybe this video would help: https://youtu.be/-lEi9DAn9rE

Quote from DMTryggr >>

He literally dragged our NPC and our sorcerer into a deadly situation because she had to hold onto him in order not to fall to her death (he was tasked with carrying the two to safety via the fly spell our wizard cast on them.) Rather than fly to safety, he ran headfirst into an enemy boss lair and nearly suffocated them.

I think I've spotted your problem.  Stop casting fly on him.  Stop tasking him with being responsible.  Stop putting him in a position where he can endanger you.

Understand that anything other than a stand-up fair fight where there's a chance of your PCs dying as well is going to lead to hard feelings with Dave's player.

Ask yourself the uncomfortable question:  Is everyone in the group this upset or is it mainly you?

But back to your original question:  How do you insta-kill a level 20 barb?  Almost impossible.  

Cast fly on him, tell him to cross a pit of lava, uncast fly.  Assuming you're all level 20, polymorph him into a statue and drop him to the bottom of the ocean.  When he un-polymorphs, he drowns.  Plane shift him somewhere and ditch him, he's not your problem anymore.  Promote him.  Kick him upstairs and out of your hair.  Give him a kingdom to rule and he's not your problem anymore.  Give him something he really likes, but that's very very fragile.  So fragile that the next stupid fight he picks, it'll get wrecked.  Once he has some personal stakes, he might get more reasonable.

Barbarians don't have great saves across the board. Feeblemind then Plane Shift to the Astral Plane. He'll be stuck there for a month with a movement of 1. Or, you know, if he's not an elf then he probably sleeps, and you can just go for a minimus confinement version of Imprisonment. Or Plane Shift to a Demiplane that the party wizard created. Maybe it's loaded with Glyphs of Warding waiting to go off.

And even if the demiplane doesn’t have any traps, he’s still stuck there unless your wizard chooses to let him out. 

.....this behavior has continued up to level 20, and your DM hasn't don anything beyond plot armor to deal with it?

Your DM should have had a long conversation with the player (not the character) quite some time ago about how their "play" is driving all the other players to the end of their rope.  It almost sounds like a situation where the DM needs to flat out eject the player.  They are actively disrupting the party "just because".

This is something you should address to the player, not the character.  It sounds to me like you have a problem player, not a player who happens to be playing a problematic character.

We've tried and he last night apologized to our party member he endangered, but said he refused to apologize for his actions because he plays his character to the extreme because he "thinks like dave" and then said he shouldnt have to stop roleplaying just because we don't like his decisions, which is essentially "i apologize, but im not sorry." He's a dick, and always has been, but even so, when he doesnt play barbarians that charge in blindly, hes never been a problem, ever.

The DM apologized after the session as well, saying he was fully ready to kill him had he not found a way out, but he's new to DMing, and thus thought he had to at least give him a chance, which is untrue. He authorized "deadly force" to allow us to sort it out ourselves, because he feels our characters should be the ones to do it, (unless he willingly walks into a meteor shower, who knows.) since we as players, and us as characters, really do not consider him an ally at this point. But he will be having a talk with everyone next session to try and save the trouble, essentially saying his extended travel with us has mellowed him to make better decisions, and that he will not allow anything that doesn't fit that character development without good reason. (because this player had actually said that about Dave before, but wrote it off suddenly the past couple of sessions)

We do have a plan A now, though. Imprisonment. put him to a deep sleep with imprisonment, rift over to the elemental plane of air, drop him off one of the floating islands, let him plummet to his death. We recently found out last session what happens when you fall there, and it's certain death. (our wizard decided to test it and waste his clone.)

Should he succeed on the Wizdom throw, its roll for initiative and at that point we figure Hold Person is our best bet, since i can go Invisible (i'm an assassin with greater invisibility infused into my dagger, twas a difficult thing to obtain.)

Then all of the rest of you tell him that you’re not playing with him and he’s not welcome because he’s being a dick, you’re playing to have fun, and he’s ruining your fun. If the DM wants to run a solo adventure with just one player he can, or he can play with the rest of you. 

Killing off a character is not an answer that works, never has, never will. This player is using the game as a tool to get out their childish antics, much the way other players use this game as a tool to become a greater version of their imagined self. If you kill off this character then the player will simply roll up a new one and find different ways to be just as childish, there's no stopping them by killing a character, you can only stop the player. If you take away their toy, they'll get mad, feel personally attacked, and lash out even harder.

I reiterate: Killing the character will not stop this from continuing, it will only make it worse.

Talk to the player, plainly, explain in very simple terms that their actions are causing problems in, and out, of the game. They will almost certainly respond with something along the lines of "It's what my character would do" and you need to expect it. That argument is accurate in some circumstances, but you can easily point out that a barbarian isn't stupid and would consider the safety of their party members. Unless they have a Wisdom/Intelligence score under 6 they know right from wrong, they know friend from foe, they know how to be civil, they know that they have different skill sets than the other party members, and rage does not mean kill everything in sight since he's not randomly attacking party members. 

Then, after that conversation is over, again in simple terms, explain that if they continue to act out, they are no longer welcome at the table. Done.

Killing the character will not stop this from continuing, it will only make it worse.

I think as well, the DM should not give the players the responsibility to deal with a troublemaker, hut should decide himself to simply kick him out of your game. On the other hand all of you, but the DM and the troublemaker, could leave the session as well and build a new roleplaying group with less headache. One of you can try being the DM, or you change from time to time that everyone can give it a try.

The easiest would be to kick players being a nuisance to everyone out of the game, and I reiterate the DM should have intercepted way before.

Sounds like an issue of the player, not the character itself. You can let him draw from an invisible Deck of Many Things and Donjon him, or perhaps just have a chat with the guy out of character and explain that he isn't meshing with the table.

Quote from DMThac0 >>

[snip] ...explain in very simple terms that their actions are causing problems in, and out, of the game. They will almost certainly respond with something along the lines of "It's what my character would do" and you need to expect it. That argument is accurate in some circumstances... [/snip]

 "That's why my character would do" is acceptable on the odd occasion to explain creation of some tension or drama. It's not acceptable to resort to if you're justifying weekly ass-hattery.

The reason it's acceptable occasionally is that it doesn't negatively impact on the fun of other players - it's a genuine and enjoyable part of the game, which everyone gets to engage in. Friction makes role playing interesting.

The reason it's not acceptable as just a standard part of play is the pretence that the ass-hattery is somehow coming from the character, forgetting that the player chooses the character. A character is not some objective, tangible, actual creature. There is literally an infinity of potential characters inhabiting this world you're exploring and the player is allowed to role play as literally any of them - so if the player is choosing to role play a character who has no choice but to piss off the other characters (or players), you have to acknowledge that it's their active choice to do so.

If your player is determined to hide behind "that's what my character would do", then explain to them that they are playing either the wrong character or the wrong campaign. They get to choose which they prefer: a character who behaves in a way that doesn't damage other people's enjoyment, or a campaign at a table where his behaviour is more welcome.

I've had players with characters like this. I usually don't have to solve the issue if I am DM'ing, my other players do; usually by letting him charge in and get himself killed.

I had one group that kept the stabilized character unconscious the whole session. He eventually stopped joining the group because the other character wouldn't heal or assist him after he almost got them killed.

In one campaign I ran, where we had this type of player and he was endangering the party, and the party rogue in particular, the rogue began systematically poisoning the problematic character and made it look like the enemy boss who was after the party was responsible.

I, myself, as a player have run into issues with this type of player more than once in my 30+ years of D&D. Solving the issue usually depended on whether the character would listen to reason, my characters alignment, and the other party member's attitude towards the character. If I am playign the healer, I usually inform the character that I won't be healing him. I've actually had such a character attack me and almost kill me after making that threat.

There are many ways to deal with such a situation dependign on the other party members and the DM.

If he's committed to "playing his character to the extreme," let him.  Let him charge into battle. Just don't follow.  He does something that runs afoul of the town guards or his counter to everyone elses' alignments?  Turn him in (or at least don't back him up) and say you're "just doing what my character would do."  Let his own poor decisions do him in.  You guys killing him off will solve nothing - you and the DM have to let him suffer the consequences of his actions.  That's the only way he'll learn. 

Pick a fight with a massive enemy and leave him to fight it alone.  If he wins YAY if not, oh sorry.