People "theorizing" that Kirby can beat Sheik really doesn't mean anything. As it is, she has zero bad matchups and many good ones. And Sheik certainly isn't the only character to struggle against heavy characters. The difference is that Sheik always has the option to run away and throw needles, which none of those characters have an answer to. The "Sheik can't KO" argument also always rings hollow and desperate to me. Her forward smash and down smash suck. Her back air can't KO anymore. Okay. But she has a reliable up air, her forward air KO's at 150%, which means characters surviving to 200% or so is a non-issue, Bouncing Fish is strong, versatile, and basically safe off-stage. Her up b is incredibly safe at almost every point of the attack and has a huge explosive hitbox that KO's. That just sounds like she needs to do more damage to get her KO's, which obviously makes sense given her ridiculously safe damage output. To say she "struggles" is kind of insulting to characters who actually do, like Pikachu, Game and Watch, even Greninja, since he lost his up air vacuum and all of his moves are quite slow and unsafe without perfect spacing.
Rosalina being KO'd at 60% is quite an exaggeration aside from what, a Captain Falcon sidesmash at the ledge, which KO's more characters than it doesn't. Rosalina's weaknesses are also mitigated somewhat by her having a strength no one else has, that she's incredibly difficult to approach OR zone due to Luma absorbing hits, and that you can't even pressure her because of Luma recall. She has weaknesses, obviously. But she has strengths that require you to play in a very specific way to have any chance at all against her, which is a big deal and makes for some incredibly lopsided matchups.
The thing with those two is that their "bad" matchups aren't bad in the sense that any character has a bad matchup. They're "bad" in that they aren't able to dominate as so many of their other matchups go. They're not exactly going to push Sheik/ Rosalina players to get a secondary, aside from pre-patch Diddy vs. Rosalina.
bolded, because i want to really discuss this.
People "theorizing" that Kirby can beat Sheik really doesn't mean anything. As it is, she has zero bad matchups and many good ones.
Kirby's CQC game is very potent, with fsmash being a strong, quick punish, his Utilt leading to juggles, Dtilt with shield pokes and trips, Ftilt with pokes and tilts, and his grab combos. all of this deals more damage than sheik can do to him, since she has horrible damage output (which can lead to people trying to look for a trade against sheik more often, since they will be on the winning side of the trade), and she can't needle him, since kirby's crouch is the best in the game along with jigglypuff and others. but, once he gets needles, he gets 1.0 from what i've heard from other players, which means better needles than sheik. that means,
he can play sheik's own game better once he absorbs her.
if this doesn't even hold true, it highlights a sign that legit counterplay is being found against sheik, or better,
counterpicks.
The difference is that Sheik always has the option to run away and throw needles
hmmm.
sheik's long ranged options are, needles, bouncing fish, and grenades.
Needles- if you get hit, it's 10% and it doesn't push you back far at all. not to mention sheik has to charge them to produce the same effect of pushing you back any real distance. a single needle is just disruption and you can get closer to her even quicker. needles can only go 2 angles. horizontal and diagonal. horizontal isn't very effective at true camping as, it gets beaten by shields, jumps, getting hit trying throw them out, and you can beat needles by
getting hit and keep running. sheik isn't toon link, nor is she Duck Hunt, Olimar, etc...
Bouncing fish- if i bait you to throw that move out, you're dead. if you hit my shield, big woop, i just close in on you and make you do something. if you hit me with the move raw. i better be at a high %, offstage, or luigi, because i'm
coming for you.
Grenades- take setup time, doesn't active instantly (both pro and con), and sucks you in. Built to be a trap move instead of zoning tool.
Three options that can be dealt with by
any character in the game at a distance. Close combat is more troublesome however as sheik has the best defense in the game. But, once you corner her, she has to conform to your game as she'll have limited options once distance space is correctly utilized