Tough one to identify exactly where he slots in. Mark can't come close to the best of them, but there are a loooooooot of them. Someone other than me...
the only opponent goku and co. have faced that could be considered on that level was jiren and they fought him in a tournament setting. moro, granola...
I mean I can't really say for sure they only had the 1 fight many power ups ago the big bads he has fought seem to at least be around beerus in power...
So between SF3 and SF6 Akuma has been going around doing fights to the death and murdering people, because that's pretty much what the PS blog about...