Rosalina would be higher if more people played her, but you can't expect that from such a boring character.
Why do you do this to me?
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Also to add to a different topic,

struggles a fair bit with the following characters;




. These characters exploit one thing that make the MU's real tough for her.
Link and Toon Link are projectile zoners that limit her burst movement and ability to approach, which is still only average at best.
Luigi can do similar with Fireball, and has legitimate combos and followups that cannot be escaped with Bat Within, but most notably he is one of the only characters that can
legitimately edgeguard her thanks to Luigi Tornado gimps. To a lesser extent, he can also challenge her aerial approaches with intangible head Up Smash. By far one of her worst MU's, with what I would argue is Toon Link.
Ness does well against her because he is a perfect weight and has great floaty air physics to easily escape her combos, and his main KO method is low commitment and avoids Witch Time (Bthrow).
Other characters with similarly strong zoning and kill throws, such as

and

are also pretty tough, they are debatable.
Characters such as

and

are also bad MU's for various reasons, mainly banana and actually safely KO'ing Sonic.

handles Bayonetta just fine (still likely even), for similar floaty and zoning reasons. Finally, characters with good counter moves that can space around her (

/

) also have a claim to fame of being able to edgeguard her well.
Bayonetta is far from invincible. Yes Witch Time and combos yadayadayada but she has a nice chunk of troublesome MU's.