And this is why Super Man games, comics and movies all suck. Batman is much more interesting.

First off. Kirby can't beat anyone. Seriously, Elektra could probably beat him. Kirby can't suck up any particularly strong enemy that puts up a fight, and not every enemy gives him an ability. Even a guy like Poppy Bros can't be sucked up until rendered unconscious.

As for who could take out Marvel's more powerful characters... not many. Samus could take out guys like Spider-man, and maybe Iron man. Would lose to guys like Thor. Mewtwo's psychic powers make him formidable, but Marvel's psychics outclass him. It's also pretty unclear, if we go by games, what limits he or any other Pokemon have. They claim to be universe creators and such, but can be hurt by average Pokemon. I'm actually just going to throw out Pokemon altogether.

Shulk *spoilers* could theoretically take out the Marvel U as a whole. The Monado literally controls the fabric of the universe, so if its potential was unleashed Shulk could literally become god. He is conceivable as powerful as infinity gauntlet thanos, but he doesn't show that level of mastery in the games. There are marvel characters with similar abilities (scarlet witch) who are more adept at using them, even if not as powerful.

Unless we want to count Bayonetta, there isn't anyone in the Nintendo U I can think of that can physically compete with the Hulk, Sentry, Juggernaut, or Thor. Few characters that can really compete with lower powered heroes like Spider-man or Captain America.