Are we talking about Ganon? I maintain that Captain Falcon's moveset without a good dash speed is nearly hopeless. They took away speed and added power, but speed is worth much more than power in Smash. Hilariously more, in fact.
Ganon's problem is that he doesn't hit hard enough. I know that sounds absurd, but hear me out. Ganon hits like a truck filled with other trucks, but he has almost nothing in the way of guaranteed followups. All his moves are incredibly powerful, but they exist in isolation. This is in contrast to speedy characters, who can typically chain moves together to great effect. Most good characters in Smash's history have been capable of sick-nasty disgusting combos, and Ganon just isn't built for that. The areas in which he's strong are not the areas that are essential for high-level competitive Smash.
I have an analogy here: I was a rower for many years, and whenever it came up in conversation, someone would end up saying, "Hey, I'd probably be a decent rower. I've got some strong arms." Well, actually, rowing is almost entirely reliant on leg strength. People just had the wrong idea about what was optimal for the sport. Similarly, a Smash character whose every move knocks you halfway across the stage isn't really what you want. You need to have the ability to link moves together. Ganon can't do that in any way that's reliable. In order to make that style of character viable, the reward for even a single hit would have to be insane, since they're proportionally so hard to land (How much harder is it to land Ganon's fair than Sheik's? In light of that comparison, do you think the reward for landing Ganon's fair is large enough?). The obvious issue here, from a game design perspective, is that he would become the most disgusting noob slayer in the history of videogames, banned in household Smash across the globe. It ain't happening, friends.
Also, his recovery is turrible. One of my beefs with Little Mac is that I just don't think an awful recovery is good game design. It's too vital a part of Smash's gameplay.
Done waffling. /WarandPeace