psh. 5e paladins will consistently do the highest nova damage of any other class hands down. because of how their smite works and interacts with crits. blade warlocks have the closest chance of catching up to them, but eldritch smite doesn't work the same as paladin smites. a 17th level fighter can also throw down a TON of damage in a single round depending on if they have a strong weapon, and including action surge, but they can only do that twice before a short rest at that level. which is still significant, don't get me wrong.
slight tangent, i feel like people underestimate fighters in 5e. casters always come across as godly, especially at high level where they are throwing around reality warping magic, but there is a limit to how many spells they can cast. a high level fighter can attack 4-6 times per round EVERY round ALL day long. even with just a regular old longsword, that's still potentially at least 4d8+12 (assuming a 16 str, which there's no reason for a fighter to have 16 str at lvl 17). what's more likely is a 2 hander with great weapon master and a 20 strength, and now it becomes 8d6+60 (also assuming they hit, which they wont always, but a caster won't always hit and will often only hit for half damage from a resisted spell)
paladin smites can be used with every attack they make, and you can decide to smite when the attack hits so you don't use up a spell slot on a missed attack, unlike wizards who if they miss, they just wasted a spell slot. warlocks can chose to eldritch smite on an attack, as well, but eldritch smite costs a bonus action to "activate" so they can only ever do it once per round, and never on opportunity attacks. on top of that, at certain levels, paladins start auto-smiting. their base attacks just start doing extra d8's of radiant damage, not to mention that their smites (base AND spellslot versions) do extra damage against undead and they'll start doing anywhere between 2d8 and 9d8 damage PER ATTACK depending on spellslot level and whether or not they are fighting undead ON TOP of their weapon damage and whether or not they have great weapon master. now you crit and double that. this is one of the reasons why paladins multiclass so well with sorcerer because you get spell slots a lot faster, AND can use sorcery points to refresh smiteslots and your party will be lucky if there's anything left when you're done.
