is that attack claw? cause fair is so freaking easy to shield grab (for marth at least)
In my experience, Bowser's guaranteed loss matches are against Marth and Jigglypuff.
He literally can't do anything to either of them if the player is even remotely competent.
Please note that I'm not ragging on Bowser here, I actually like him and have been playing him quite a bit recently. It has served to make me painfully aware of his faults, unfortunately, despite my efforts to correct them.
He really does not have the advantage in
any match. Kirby can at least break even or possibly eek out an advantage in one or two matchups, but every fight with Bowser is uphill. He does not have any safe approach options, his recovery is terribly predictable and easily gimped, he can't safely trade aerials at all, and he's so big that he's complete combo bait- even for characters who can't combo normally.
He has great KO power and arguably the best OoS option in the game, but the former is outweighed by his extreme slowness and the latter with the fact that that's basically the only thing you can do (he can't even shield grab effectively).