Ultimatum479
Smash Apprentice
Fox is a valid counter. His reflector makes your Forward-B useless and dangerous, and he beats Oli at his own game of racking up damage. MetaKnight isn't too bad against Olimar, but his light weight makes him vulnerable to Oli's godly up-smash for a quick KO. Sonic and Wolf aren't counters at all, as I'd know because I just spent an hour playing against each yesterday. Sonic is horribly predictable; all of his roll moves are easily dodged and Oli can even grab him out of it due to the absurdly long grab range of Pikmin. Wolf is slow enough and Oli's killing potential is better such that you can successfully trade hits with him to a KO.