D&D PvP: How to balance one powerful vs two weaker players.

I'm wondering what levels you think would work best for pvp in a dungeon or other unique environment (possibly multiple rooms and props) if it's one more powerful player vs a team of two weaker players.

Would a level 5 with an uncommon magic item of choice vs two level 3 players be an even match? I figured without the item level 3s multiple turns and potential synergy would be a more likely win, so I buffed up 5s raw power with an item but felt level 6 with no item would be too powerful because of D&D scaling.

What that work, and what other levels could work for this? I want this to be as even of a match as possible.

*Edit:

I understand 3x3 v 5 may not work, I'm wondering if any levels are at least fairly balanced. These are players who want a PvP arena, not players who in a normal campaign got in a conflict.

They are aware that PvP can be very fast paced, which is also why there are multiple rooms and props: it adds ambush tactics and such. Think of it like those gun duels in some Hollywood cowboy movies where they dramatically stare each other down, then both draw their gun and quickly fire. It can end right there, the winner being whoever drew faster. I want to make these battles longer but I'll settle for that if needed.

I should also state that each of the 3 can choose to start in a different place, so the two teammates may not necessarily be together if they don't choose to be.

So my players are not fighting, and I am not forcing my players to kill each other. This is for the people who actually like fast-paced D&D PvP, who want something new and more interesting than a 1v1.

It's been said many times before but D&D really is not built for good PVP and trying to balance it is extremely difficult.  Just stating "one level 5 vs two level 3s" is impossible for any of us to determine, since it doesn't say anything about what the characters can actually do, their ACs and HP, or any other information that would influence the outcome of the fight.

The two things most DMs go out their way to avoid is players at different levels and PvP so the obvious question becomes how did you even end up in a situation of two level 3 trying to fight a level 5? 

Level 5 characters are absolute beasts compared to lower levels, the jump couldn’t be more noticable. Not only do Martials get multi attack which doubles their output to beat two level 3 characters, but spellcasters have way more options to just stop the other low level PCs from even mattering.

I'm wondering what series of mistakes led to this situation in the first place. Fundamentally you can't balance PvP in this situation. As the others have mentioned, D&D isn't designed for PvP. It doesn't have the kind of rock-paper-scissors advantage negation design baked in and that's a feature, not a bug. D&D is designed as a collaborative storytelling adventure game. If your players are engaged in combat against each other something has gone terribly wrong.

The only way to balance PvP in D&D is to go the IROC route by removing all the variables and assigning all competitors the same loadout. In D&D that would mean everyone plays Xerox copies of the same player character: same species, class, subclass, equipment, feats, spell list, stats, etc. And it would mean even numbers in 1v1, 2v2, 3v3, etc., or an all-out free-for all with no teaming up allowed. A 1v2 scenario wouldn't even work under these restrictions.

So I guess the advice is either accept that there is no way to balance what you're looking to do or... just don't do it?

What is the situation here?

Is this a narrative match like the "Recruit the villain" or " we got the wrong guy" tropes?

Is this PvP because the players couldn't work together?

Is this a case of a villain is given a player to make it more interesting? 

All these situations have different solutions.

Like others said, you can’t balance it. PCs are glass cannons. In D&D, PvP really comes down to initiative/action economy, owing to its turn-based system. I win initiative, and I get my nova attack off before you do. I probably win. If I don’t, and I’m still standing after your nova attack, then I get to go again before you do. 
And stealing the other side’s action economy is what will really win the fight. If the level 5 is a wizard, throw out a hypnotic pattern, move to a safe distance, and leisurely take out one target, then the other. If one of the level 3’s is a cleric, cast hold person on the level 5, and the fight is over.

The whole thing will not be as satisfying as you might think. 

Assuming everyone is on board for this and (hopefully) it's just a fun little deviation from the actual story... you're going to have to "white room" it yourself multiple times. You cannot balance it by loadout alone, as there is already so much imbalance and too many variables even before individual player decisions come into play. In your example, how are you going to know whether the item you (or they) chose is actually going to benefit? I'm with everyone else here: why subject you and your players to this, as it's clearly not designed for such a thing.

I will say that I have seen DnD PvP done, and it was somewhat entertaining, but that was with an incredibly experienced DM, environmental factors that were just as powerful (if not more powerful) than the PCs were to even the playing field, and a group of players who were just doing it for the lolz. Even then, I don't think that many people who watched were all that surprised that the sorcerer won in the end.

D&D PvP is extremely random, particularly for small numbers at low levels. There is a significant chance of a level 5 vs two level 3s ending in one round, with either side potentially victorious. On average I think the level 5 would have the edge, but it's fairly close and depends a lot on die rolls and the specific classes involved.

The game isn't made for PVP unless the players from the start know they are going into PV - like an arena style game.

A DPR build will dominate most conflicts against an RP build, not a fair contest.

In session zero I always tell my players that here is no PVP. There are other ways to settle disagreements.

To give an example: consider a level 5 draconic sorcerer, with spells such as lightning bolt and fireball. A typical point buy build will have AC 15 (20 with shield), and 37 hp. Save DC is 15.

Most level 3 PCs have fewer than 28 hp, and thus on a failed save will be dropped. Since this is a sorcerer, a quickened cantrip has a pretty good chance of finishing off a survivor.

Of course, this sorcerer also likely has a terrible wisdom save, so if a level 3 wins initiative and casts hold person, being beaten to death without ever getting an action is a real risk.

Quote from Pantagruel666 >>

To give an example: consider a level 5 draconic sorcerer, with spells such as lightning bolt and fireball. A typical point buy build will have AC 15 (20 with shield), and 37 hp. Save DC is 15.

Most level 3 PCs have fewer than 28 hp, and thus on a failed save will be dropped. Since this is a sorcerer, a quickened cantrip has a pretty good chance of finishing off a survivor.

Of course, this sorcerer also likely has a terrible wisdom save, so if a level 3 wins initiative and casts hold person, being beaten to death without ever getting an action is a real risk.

 Nitpick: The Fireball needs to be the Quickened spell. 

Other than that, all correct.

Given everyone a week of downtime and just roll. It balances. If someone died they got unlucky with initiative which is fair or didn't plan for the battle and died unprepared. Just make sure no one is playing an Alchemist because they are broken and can kill everyone before their Initiative.

… How exactly is an Alchemist Artificer so fundamentally broken?

I was wondering the same, only time I’ve heard them described as broken before was people bemoaning how bad they were compared to the other Artificer subclasses 

I imagine they're about as broken as elves are evil or dumb.

Quote from sabin76 >>

I imagine they're about as broken as elves are evil or dumb.

 Fact, they are extremely broken.

Quote from CunningSmile >>

I was wondering the same, only time I’ve heard them described as broken before was people bemoaning how bad they were compared to the other Artificer subclasses 

Yeah, I thought they got weaker but they are still the strongest class in the game. I just had to get more crafty and think even further outside the box. The Alchemist Love Bomb is a sound tactic. Better living through chemistry!

Quote from heydanseegil >>

Yeah, I thought they got weaker but they are still the strongest class in the game. I just had to get more crafty and think even further outside the box. The Alchemist Love Bomb is a sound tactic. Better living through chemistry!

 Crafting a philter of love is no more effective for an alchemist than any other class, it just takes half as long, and there's no special way to force someone to actually drink it. Any class is broken if you ignore the rules.

Quote from The_Ace_of_Rogues >>

… How exactly is an Alchemist Artificer so fundamentally broken?

Shoot I meant to reply to this. While it may not be as helpful in a PvP immediately upon making the character it will if the character has significant down time.

Alchemist make potions and they can be built to craft them three times as fast with the right Feats. Once they have at least 41 hit points you can begin experimenting on yourself using Miscibility which makes the effects of a potion permanent on a 100, couple that with the Human feature that provides the Heroic Inspiration and you can make two rolls on the Miscibility table turning that chance into a 1 in 50 from a 1 in 100. Start drinking two Elixirs of Resilience at the same time every chance you get and each time you gain the permanent benefit it not only stacks but has to be individually dispelled.

I got my Alchemist to AC 30 from AC 10 in under a year of downtime but you can do other stuff too like give yourself permanent dragon breath or whatever. The only draw back is the amount of prep time makes it impractical in most campaigns but if I get the down time and I have more than 40hp to survive the damage if I get a 1 on the Miscibility roll then I start experimenting with chemistry.

Miscibility is a DM feature, so I would say that attempting to rely on abusing it for perks will get nixxed rather quickly