I just want to know the best class and subclass for combat, specifically, for doing damage. No multiclassing whatsoever. Feats, sure. Race sure. I currently play fiend warlock with pact of the blade. I just want to know everyones opinion really. Honestly, everyone seems to like vengance paladin, but someone, please explain this to me! 

If you play a powerful  combat-related character, please post it. 

Define doing damage; like are we talking about pure burst, sustained, damage across multiple targets...?

Because that changes the metrics quite a bit.

Also at what level? At high levels, it's a caster. At low, likely a martial. In between, I'll leave that to the people who have DPR spreadsheets.

Historically when I played through the 1990s.  Fighters did all the damage at low levels and protected the wizards and illusionists (no sorcerers or warlocks).  Then in the upper teen of levels things switched.  Spellcasters in upper 20s and 30s had so much combat power.   Back then there was no 20th level limit.  Every class had a different point level for advancing.  So if you had 500,000 XPs the wizards were one level and fighters were a different level.

Level 20, probably.

It really depends on the vibe you're going for both combat and narrative wise. I'm currently playing a vengeance paladin whose oath is based on hospitality. It's been very burst and obviously single target. I also prefer rogue, which differs in that it seems to have better sustained damage with sneak attack and any added shenanigans available from any of the subclasses. Rogues have utility outside of combat too in their skill-monkery so you're not entirely a fish out of water in non-combat situations either.

I find paladin kind of boring in exploration sections that rely on skill-checks (with no persuading/intimidating) because they suffer mediocre skill bonuses from needing so many stats. Strength for damage, constitution for health, charisma for spells, and wisdom for saves/perception/insight - the clunkiness really showing in how their half-caster-ness. Feels like a class that's very easy to fall into trying to minmax for well rounded stats to me, but you can make a very interesting character without braining out the stats (a novel idea I struggle to actually do).

Smite combined with divine favor and hunter's mark has been a fun combo for me if you can keep hunters mark up but takes a few rounds to get it rolling. Vow of enmity to give yourself advantage, or once you get hold person (if you can keep the concentration/get lucky on them failing saves) will force each hit you land to have advantage and count as a critical hit for the paralyzed condition. And critical smites are deeply satisfying. All of the abilities synchronizing perfectly is definitely situational and dependent on failed saving throws, but aside from rogue's sneak attack and cheeseball fireballs I've definitely found the vengeance paladin the most reliable in smacking one target really, really hard. Also if you use a warhammer you can push a creature 10 ft which is thematically a blast (haha) to be tossing enemies around. Also also, I think with a greataxe you can make a free extra attack (no modifier) on another enemy within 5 ft.

Feats wise you could grab savage attacker to reroll your weapon damage dice, but I didn't find many others appealing because I hate remembering that I have them since most don't really show in the combat area of your sheet. For hold person/hunter's mark it might be worth taking war caster for advantage on concentration saves/reaction casting hold person as opportunity attack.

I'm sure there's more to it than that, but this is what I've at least gathered from my experience. I've never gotten anywhere near level 20 in any long-run campaigns just for the sheer amount of bullshit we get up to at levels 3-12. 

Thanks for reading my brain soup :)

 At level 20, for straight single target beatdown potential, depending on magic items, it's probably a fighter (not sure which, they all have some quite strong high level features), mostly because 4 attacks per turn and 2 action surges per short rest. For engaging multiple targets, might well be a wild magic sorcerer (use tamed surge to do max damage with all your spells for the next minute).

I'm going to posit a high level wizard with access to a Bombard Spelljammer can either raise enough undead to man the ship and it's weapons (which will include 2 ballista's and the "Giant Cannon") or animate them directly to self load and fire will (assuming all of the weapons hit) inflict 22D10 per round (or an average of 120 damage per turn) on top of the Wizard doing horrible wizard things.

Also, when the Spelljammer is no longer within 1 mile of "an object" it instantly accelerates to a speed of 100,000,000 MPH which would cause an absolutely catastrophic sonic boom as it achieves Mach 130332.36152 and quite possibly causing an exothermic event sufficient to ignite the local atmosphere.

Single target damage martial classes do the most damage, fighter probably on top, but I think a berserker barbarian with the new brutal strike might be the there as well. Multi target spell casters, normally I'd say wiz/sor but with how the new mobile damaging zones work I'm not so sure.(the one exception is conjure minor elemental builds so a valor bard really, but I'd expect house rules while a errata is likely forthcoming)

This generally translates into martials kill bosses, casters kill masses. 

Quote from MyDudeicus >>

Single target damage martial classes do the most damage, fighter probably on top, but I think a berserker barbarian with the new brutal strike might be the there as well.

Barbarian is really really good in tier 1 and 2, but its tier 3-4 progression is mostly about toughness.

Quote from Pantagruel666 >>

Quote from MyDudeicus >>

Single target damage martial classes do the most damage, fighter probably on top, but I think a berserker barbarian with the new brutal strike might be the there as well.

Barbarian is really really good in tier 1 and 2, but its tier 3-4 progression is mostly about toughness.

I am not sure math wise how far the 4d6+2d10 from frenzy/brutal strikes will carry it along with retaliation especially given how DM dependent it is too bad brutal and frenzy are on your turn instead of a more general once per turn cause then retaliation could really shine. Assuming polearm based a fighter is doing 5 attacks vs the barbarians 3, but if the barbarian is getting attacked its 5 vs 4.  Though i guess a battle master with riposte would have 6 whenever missed. All of that is so DM dependent though so its hard to gauge. 

Though all but the extra 1d10 from improved brutal strikes is there by level 10 it seems to be a big enough damage jump over fighter at those levels that it might take it as solid into 14/15ish. Their level 20 rocks, and boon of epic combat prowess takes the sting out of losing advantage to get our brutal strike. So it feels to me like tier 1-2 great, tier 3 very good, tier 4 starts to fall off until level 19 where they can guarantee the hit that does an extra 2d10+4d6.

But I'm not a math guy, its just a general impression. 

Quote from MyDudeicus >>

I am not sure math wise how far the 4d6+2d10 from frenzy/brutal strikes will carry it along with retaliation especially given how DM dependent it is too bad brutal and frenzy are on your turn instead of a more general once per turn cause then retaliation could really shine. Assuming polearm based a fighter is doing 5 attacks vs the barbarians 3, but if the barbarian is getting attacked its 5 vs 4.  Though i guess a battle master with riposte would have 6 whenever missed. All of that is so DM dependent though so its hard to gauge.

Polearm mastery is a dubious investment for a high level build, you often have other uses for your bonus action (for example, your barbarian is probably using it to rage during the first turn of combat, and a high level berserker should really consider intimidating presence) and the haft strike doesn't scale well. Great weapon mastery is generally going to be better. Brutal strike is actually terrible, losing advantage frequently costs you more damage than +1d10 will give you, though it becomes worthwhile once improved brutal strike kicks in. The other major factor is how many rounds of combat you assume per short rest, because action surge is insane. Doing basic math, assuming:

• +3 weapon. Not going to use polearm mastery for now, so we'll pick a 2d6 weapon. There are no particularly great masteries available.
• great weapon mastery.
• Species unspecified (I like cloud giant goliath because a lot of problems can be solved with teleportation, but human for an extra origin feat is very solid)
• (barbarian) berserker subclass.
• (fighter) blind fighting fighting style (great weapon fighting is terrible)
• Max strength
• Epic Boon: I think Combat Prowess is the most effective, it triggers somewhat more often than irresistible offense.
• Assuming an AC 20 target.

So, let's do the math on the barbarian

• Attack bonus is 16 (+7 for strength 25, +6 for proficiency, +3 for weapon)
• Base Damage is 2d6+14 (+7 for strength, +3 for weapon, +4 for rage) or 21, increased to 27 (great weapon mastery) if part of your attack action.
• First attack uses improved brutal strike for 38 with an 85% chance to hit, which is actually 100% due to combat prowess, for 38.
• Second attack is normal (brutal strike is once per turn) with 99.7% chance to hit (only way it misses is if you missed with advantage and you missed your first attack), for +27.
• Critical hits add 1.6 dpr, and may trigger your bonus action extra attack, if it's not otherwise used and you want to use it on this (up to about +3 dpr, but usually less)
• Frenzy does 4d6 for +14.
• You will probably (call it 75%) get either a retaliation attack or an opportunity attack. This can be assumed to do +21. This can be increased by having sentinel fighting, but with only 5 total ASIs to play with, that may not happen.
• Total dpr: 95

And for a fighter (battle master)

• Attack bonus is 14 (+5 for strength 21, +6 for proficiency, +3 for weapon)
• Base Damage is 2d6+8 (+5 for strength, +3 for weapon) or 15, increased to 21 (great weapon mastery) if part of your attack action.
• Four attacks at 75% to hit, but one miss will be negated (average 3.71 hits) for a total of 78. If we use our relentless d8 for precise attack (if needed), and use it for damage on the last attack if not needed, this will on average get us 0.19 extra hits and 3 extra damage, increasing our total to 82. Critical hits increase this marginally, to 83, and give us a chance of an extra attack (which we may not want to bother with, it's not a lot of damage).
• Odds of a reaction attack depends on maneuvers -- there's opportunity attacks, brace (if Tasha's is being allowed), riposte (doesn't trigger that often at this level as you don't have a shield and monsters tend to have massive attack bonuses), and sentinel (with 7 ASIs, more feasible). We'll call it 40% and use our relentless d8 because there's no reason not to. This adds another 7 dpr, bringing our total to 89.
• All of that is without resource expenditure. We have an additional 6d12 from mastery dice (value depends on how used; won't be less than 39 damage but can be considerably more; best damage use is generally accurate attack) and two uses of action surge (value depends on whether we already used combat prowess and need to use accurate attack; typical value around 140 damage). If we assume 6 rounds of combat between short rests, that's another +29 dpr, getting us up to 118.

Thanks! But I guess it would be much harder to calculate the DPR of spellcasters versus martials, as spellcasters have a limited number of spell slots. For example, warlocks have a very low number of spell slots, but a battle master at level 15 can go on with d8s basically forever. At high levels, the barbarians rage would go on for a very long time even without having it extended. 

If there was an easy cut-and-dry answer to this, the game wouldn't be very interesting. And doing X damage to a tofu block in an empty room doesn't really tell you a lot about how a build is going to play in a real game.