Yes I’m power scaling, fuck you.
If Viltrumites (from invincible) invaded the OPM universe, how much effort would Saitama have to put in to defeat them? Each and every one of them basically scales the entire universe, so I can’t imagine he’ll be able to one shot all of them, but would they give him the fight he’s looking for?
I think the opposite, they’ve been shown to take damage and die. I think he one-shots every single one. I think they’d be perfect OP adversaries because they’d wreak havok on all other heroes and then Saitama could just yeet their heads off.