Both from marvel
Mikaboshi as in Chaos King? or how he was before becoming CK? Scathan to me a a PIS machine character and that entire arc was simply stupid. Him holding Protege after him absorbing the powers from the LT while LT himself first needed approval to attack Protege is just idiotic. IIRC CK/Mika was only a mere aspect of Oblivion and the general opinion of most people is that LT is above every Abstract being like Eternity/Entropy so if LT is stronger than Oblivion that he should have no problem dealing with a mere aspect of him, and if Scathan is in LT's league that Scathan would also beat Mika/CK.
There's no anime character here. There must be or it isn't allowed. For the actual battle, I think Mikaboshi. I'm not sure though. I don't know Scathan very well.
Scathan only had one appearance and that was muzzling a mutant that would be God. Quite honestly, bar the Tribunal / Eternity allowing him to be there - I don't think he was anymore powerful than the average Celestial. Mikaboshi on the other hand destroyed most of the multiverse / absorbed it into him.