Did anyone see RelaxAlax's video?
Yeah. It was actually decent. One of the things that really stood out was when he said that Diddy Kong and Banzo/Kazooie were featless, when a quick google search will show a bunch of feats. I also remember him putting Ice Climbers in the same tier as Lucario and Greninja, while Charizard was a tier higher than all of them for some reason.
He puts Kirby like 3 tiers above Meta Knight and Dedede when they're all relative in power and should be in the same tier (which is admittedly a mistake a lot of people make). This is especially weird since the one Kirby feat he brings up to justify his spot also blatantly applies to Dedede and Meta Knight. There's other stuff like Palutena being extremely high "because she is a goddess."
It's pretty clear he just made the list by looking at the characters and guessing how strong they look based on limited knowledge and maybe a quick look at a few threads like this one. Ironically it's actually better than 95% of charts I've seen though.
I would make an updated tier list myself to show what I think it "should" look like but I'm lazy and I don't have enough knowledge on a lot of characters to really make it.
Either way after some recent finds made by people in this thread I think that the answer to "Who's the most powerful in canon?" Is pretty clear at this point:
If were counting the super high end showings of the Mario cast, then it's the Mario cast hands down (with Bowser being the most powerful among them, probably).
If we're not counting the super high end showings from the Mario cast then it's the Kirby cast since they're confirmed universe level and can outspeed/outhax the other universals (with Kirby being the most powerful among them, probably).
So basically it's Bowser or Kirby depending on how you look at the question. Hero and the Belmonts might be able to take the throne from Kirby but I don't know enough about their universes to say otherwise.