The Marth matchup isn't terrible. I've never had too much problem in a Marth player before, but I can understand why people would think it would be really troublesome. I'd say the matchup is probably 55-45 in Marth's favor. If any matchup gives him a problem, it's Meta Knight, because Meta Knight can cover Marth's weaknesses a lot more while still being able to outspace Wario with little problem.4. Wario (He only has a couple of matchups that aren't in his favour, the most obvious being Marth. Many of his other matchups are near even or in his favour. He kills well, and his aerial DI allows for his aerials to be safe against a lot of character. Oh, and you can essentially run away and win, because a fart is the ultimate punisher for landing lag; you can bait an attack and essentially punish it with a KO).
Dedede is unfun, too, but I blame the character for making Wario players have to run away so much.