warpriest, can swift action fervor buff each round to get stronger each round.
So can Magus if they cast a buff spell instead of an attack spell with Spell Combat.
Kineticts get stronger as they take burn, although I typically take enough to cap my Elemental overflow at the start of the day if I can, because re-calculating mid combat is annoying.
Inquisitors activating judgement then bane
Investigators with the Timed Strike Talent gain +1 point of damage each consecutive round they study the same target.
+1 on the second round, +2 on the third, and so on.
There is a Mythic thing that gives you one more sneak attack dice for every attack you land in a row and the mythic rank 10 Trickster ability is enemies are always flat footed.
So you could in theory attack every turn and try and stack up some ridiculous sneak attack damage.
Might be called bloody streak or something?
Captain Obvious answer: every class, you have potions, spells, magic items... whatever that buffs you.
Tryhard serious answer: like the enemies on Zeboyd Games? Where stats grew stronger (+10%, +20%, 30% and so on) at the start of every round? I can't think of anything like that, maybe Mythic, but I doubt it.