Saitama. ONE himself has said that at his normal levels, Tatsumaki(Terror Tornado) would beat Mob. But he said nobody knew the result if Mob went ???%. However, Tatsumaki is nothing compared to Saitama and can't even lift him because apparently he's too heavy. So Mob will probably be paste before he even gets that far.
I'd say he surprises Saitama, and takes maybe more than one punch to take down due to an impressive barrier, but I still doubt he'd win. It might actually make Saitama feel good about the fight though.