How was he nerfed exactly, where was that stated? As i said many times before, it's just how Marco's power works he can even fight someone stronger than him or two guys at the same level and he can hold his own for some time because his regen is hard to deal with, you have to hit him so many times to be able to cause lasting damage, even Kizaru that's probably a stronger fighter than Marco needed seastone otherwise it would take a big amount of time to deal with Marco. King is currently fighting Marco alone, and it wouldn't surprise me if they're in a stalemate
busy with work right now so im not gonna go hunting for panels. in ch 997 or 998 or 999, marco uses his flames to stop the ice oni virus from spreading. chopper even thanks him for buying him some time. the next time we see marco when he ragdolls king and queen, he comments on how it is tiring and tough to hold back two commanders worth over a billion and asks chopper to hurry.
point being he wasnt at his full strength yet he ragdolled king and queen.
my point about king (which i said numerous times before) is if oda brings in things like awakening, advanced haki, CoC or some ability due to his race, in his fight against zoro ~ it literally shits on the previous writing where king was disarmed by izo and couldnt do anything when kaido was attacked, and when he got ragdolled by marco and when momo was saved by sanji from right under his nose.
stop defending shitty writing from oda by giving in some weird justification for king 2v1-ing marco and getting ragdolled. he should be doing better than this. if these are the standards for yc of the beast pirates, then the bar is on the damn floor.