Let us discuss the characters we have felt were the most broken over the years. While at it, we can also discuss the weakest (Ganondorf lol).

I remember playing ice climbers on melee and trying to learn wobbling, which was an absolutely broken mechanic that made playing against them practically impossible.

They are still my favorite to this day.

Ganondorf being the weakest isn't a meme at all. He may have the deadliest attacks, but his speed and jumping are absolutely horrible which greatly reduces his overall usefulness.

One character I'll never understand is Jigglypuff. He's so light that he can be pushed away with extreme ease, his attacks are nothing out of this world... He's basically the character I use for the "Beat the game in the easiest difficulty" achievement because I don't dare to use it in any other way xD

One of the most broken characters, at least was in the past, is Fox. His reflector back in Brawl made him invulnerable to non-physical threats, and it rebounded attacks from Pokeballs and Assistants to the user which activated them, who would otherwise be mostly immune to its effects. You had to rely on Smash attacks and from a short distance to defeat him. And when Final Smash was first introduced, his Landmaster made things absolutely horrible.

I wish I had fresh memories of all the new additions to Ultimate, but it's been a while since I booted that game. I do know they got rid of DK's absurd Final Smash, which was a very welcome change.

I'll stick to Ultimate since I don't really have much experience with characters being broken in past games but I know he's considered the worst character in the game but Ganondorf almost always destroys me for no reason I can't explain it I'll never forget facing one of the fights in World of Light that was metal Ganondorf and spending over an hour trying to win it was awful.

Joker used to be overpowered before Arsene got nerfed so much my brother hated facing my Joker cause I could just get Arsene and then effortlessly take a stock it took a long time for him to stop getting 4 stocked by me when I'd play Joker.

I'd say I find Pyra and Mythra a bit op as well being able to swap between speed and power is crazy and it's not like Mythra can't get KOs too.