People seem to think a character has to be top tier to carry players. This is very wrong, and here's a little thought experiment to illustrate why. Picture a character that, once you pick them, automatically wins the game 30% of the time, and loses the other 70%…
This character is total trash at top level. It has only a small chance (21.6%) of winning you a bo3 set, and an even smaller chance of winning the bo5s which occur late bracket. No one playing this character could be a real "top player" in the long run; it isn't sustainable.
But for a total newbie? This character is absolutely amazing. That 21.6% chance - it's a 21.6% chance to beat any player in the world in a bo3. If my 87-year old grandma mained that character, she'd transform into an "upset demon with high highs and low lows."
Obviously no character in Ultimate, or any fighting game, functions like this in such a blatant way. But to a lesser extent this concept often applies. All a character has to do to embody it is force high-variance situations often enough to occasionally score wins.
Think of Melee Ice Climbers, Smash 4 Ryu, etc. These are characters with the tools to force guesses with huge impact - not enough to actually be consistent top tiers, but certainly often enough to cause crazy upsets on occasion.
I'd also like to note that both of these characters are by no means technically easy. Both require precision and in-depth knowledge of their characters' unique techniques. But they can enable playstyles that circumvent large parts of the skillset Smash normally tests.
It's also important to acknowledge that just because a character CAN carry someone like this doesn't mean it HAS to. E.g. We've seen countless Melee ICs that don't rely on wobbling, or slower-paced neutral focused Ryus. That's because…
The better one's fundamentals, the more consistent playstyles based on those fundamentals will be. If that 30% win button character had the alternative option to fight normally as a Lucina clone, playing that way would be optimal for top players, but certainly not for my grandma!
This is why, when I see someone respond to character complaints with "well, why don't you just play/main them?" I get annoyed. Just because X character is great at making upsets doesn't mean a good player would benefit from playing them at all. The character could still suck!
With that said, I mean no ill will towards "carried" players. Some of my favorite Smashers to watch have been underdogs who pushed a character's punish game to untold heights & kicked some top level ass (inconsistently.) And ofc some fundamentals gods make me want to fall asleep.
Not to mention that getting "carried" can let you fight better players and actually get good fundamentals (I've, uhh, been there.) Whether or not the "carried" phenomenon, within reason, is really all that terrible is up for debate & beyond the scope of this Tweet chain.
To sum up: The point I want to get across is that a character's "carry potential" is completely independent of their actual effectiveness at top level. Just another reason why single-axis tier lists, while useful, don't tell the whole story & you shouldn't treat them as gospel!