Newbie here so forgive my nieveity.

This is a question for the DMs.

Would you allow the final encounter of a campaign to be ended by with persuasion?

It could extend to a series of persuasion checks and a well thought out reasoning that is beyond reproach, delivered with perfect oratory lasting several minutes with platitudes that are relevant to the NPS boss character. -  So to make the NPC, give up , surrender , become apathetic, see the error or their ways, see that they are not in their best interest etc etc,

Or does a final encounter have to end with combat?

It's your game, so its your choice! If you think it would be fun for your players and for you, then go ahead! It should be difficult, though.

I remember a number of final encounters in games like Fallout 3 and FO:NV that can be bypassed with 'Speech' checks. These checks get progressively higher as you talk to the BBEG/final boss. These checks were usually accompanied by some serious talking from both parties and at any point in the chain if a check failed a fight would start. They work really well in the Fallout games and don't take away from the finale of the game, IMO.

Quote from VonKrauzer >>

Newbie here so forgive my nieveity.

This is a question for the DMs.

Would you allow the final encounter of a campaign to be ended by with persuasion?

 I wouldn't allow it to be ended with a simple persuasion check, but roleplayed persuasion could be fine.

You can build up to a problem being solved by anything, words as much as swords (regardless of Minsc's predilection for the latter). I don't see some powerful antagonist being convinced of the error of their ways just because the PCs wax poetically for a a couple of minutes, but if they've been working towards having good arguments that's a completely different ballgame.

"We brought you the mythical silver orb of the rising moon to prove our good will; we gave your people a reprieve from the drought that led to terrible famine; we halted the invading hordes at your borders and the silk trade you will build with the giant albino silk worms we moved into your kingdom's southern glades will have your coffers overflowing in but a few short seasons - surely you now see there is no need to turn over your throne to the cult of G'huu-sal-Kimmon the Devourer? Your citizens are safe and deserve a just and fair ruler. Turn away from the dark path, we beseech you."

That's four major campaigns culminating in a single scene, possibly over a year of weekly sessions, and now the players get to enjoy the payout. 

Quote from Ophidimancer >>

My DM threw a Death Knight at a level 5 party to use as a threat to avoid, never intending for us to kill him, but once we discovered that he used to be an honorable paladin and was actually cursed to undeath, our focus shifted entirely from destroy to redeem. With a lot of help from NPC clerics and a masterful (30+) Persuasion roll from my bard, we managed to talk him into repentance and back into the good graces of Lathander Morninglord. It was a coup that my DM did not expect at all. So there's that possibility.

I actually did a prose style recap of that session, you can read it here: The Dark Below

The evil sword unleashed an even mightier blast of necrotic energy, killing three of the Neverwinter Guard and knocking a number of our heroes unconscious. As Karash and the allied clerics worked to revive the group, the shadow knight cried out that it would never succumb to the darkness. This odd battlecry and a few other details began to resolve in Tully’s journalist mind. Could it be that the creature believed it fought for the Light? Was its mad rage a product of delusion?

Warily, the group’s tactics changed from destruction to redemption. Spells were employed to call to the remnants of the once noble spirit within, to exorcise the influence of the evil blade, and to display the might, glory, and mercy of the good Gods. Most of all, the group simply spoke to it, Fiego’s silver tongue and impassioned plea seemed to reach something deep within the monstrous form* while Tully surrendered himself to its grasp. In a moment of lucidity, it plunged its blade into its own chest. There, impaled upon its sword, a trapped and weakened voice spoke to the group. It did not have the mind to tell them much, but they discovered that in life a hundred years prior it had been known as Sir Edwin Bryce, that it could not rest because it was fighting an eternal war against the darkness, and that someone named Academician Adnelis would be able to give them more information. It was also then that the cleric, Genevra, began to hear a mysterious voice telling her that in order to release Sir Edwin from his suffering she would have to cut off the source of the darkness.

To be fair, I did have the cleric cast Guidance on me and the other Bard gave be a Bardic Die as well. That's how I got a 32 on my Persuasion roll.

Sorta like any number of Dr. Who episodes where the Doctor gets a malevolent entity to stand down.  Sure, why not?  I mean in my game's meta, I use the "Don't you think she's tired?" line in the first episode of David Tennant's run as illustrative of the power of the Whisper Bard.  The Doctor is all the Bards if you think about it.

Of course anyone who does try to intervene against a violent outbreak, set and setting are key.  Sometimes, a character may be able to set themself up as The Doctor and can convince the enemy to go the ploughshares route ... other times the PCs basically copping Starlord challenging the Kree to a dance off.  Like you might stall or give the actual combatants in your party the element of surprise, but yeah...

There are times where the BBEG fight being resolved with violence is a failure, and the only satisfying ending is when they're persuaded to do the right thing.

It all depends on context. In one adventure,.the enemy was a dragon who was hunting food. That's not really going to end in a happily ever after for everyone. However, imagine a Fable 3 type situation, a person who would be a good ruler, but has seen an existential threat coming and so knuckles down to prepare. Killing him in that situation isn't the best choice, and working together you can reach the ideal. Perhapsnyou join him, or perhaps you provide a less oppressive way of raising funds. Resorting to violence is the worst way forward.

It really depends on context. I would never make it a simple persuasion check (I rolled a Nat20, sweet, that encounter was over in a single roll), but it some situations it's best to allow a non violent means of resolution - should the party show desires for one.

I try to imagine at least two ways for each combat to go - not least so I'm ready for it! (they fight - easy, always plan that one. They talk? They avoid? They trap? They hold hostage? loads of options, usually!)

If I've lined up the BBEG to be a "fight scene", that's because I've given strong motivations to the BBEG to fight the party. I tend to plan the motivations (hunger, instinct, needing a sacrifice, fear of reprisal for not fighting, power-hunger, outright sadism, arrogence and pride, and so on), and then if the players can bypass their motivation - for example, by giving the BBEG monster food and tempting them away from the town with it - then they can resolve the story without violence!

Personally, I love it when these things happen - not least because it means that a character can come back - perhaps Ulthzor the Dark Lord is trying to run a merchants, has been ripped off by gnomes who've sold them shoddy goods, and petitions the party to help them to set up their new life and become a functioning member of society. Maybe, when the final final boss of the campaign arrives at level 20, the party find themselves surrounded by people they have saved instead of killing, who ride to their aid against the coming apocalypse, as if you planned it all along.