Stages I absolutely hate:
3D land: scroller.
Golden Plains: the coins are just dumb imo.
Rainbow Road: As nice as this place looks, cars are dumb.
Paper Mario: Confusing and all of it's forms are annoying.
Mushroomy Kingdom: No one needs to explain this one.
Jungle Japes: Something about it has always seemed off. Also, water.
Gerudo Valley: Random fire and ice that seems to one shot people often.
Spirit Train: Super confusing stage, hard to hit anything, weird gimicks.
Brinstar: This one has always been bad and ugly.
Corneria: This one has always been bad too. Plus those planes.
Mute City: It's just ugly and the background bothers my eyes.
Magicant: The red guy
Flat Zone 2: Everything
Warioware: Dumb gimmicks on the minigames, and RNG with rewards. What use is a mushroom vs a star?
Distant Planet: Absolutely horrible the first time, horrible the second time.
Find Mii: Would've been awesome without the green guy.
Pictochat 2: The stage is a tougher opponent than most people.
Green Hill Zone: Annoying layout.
Wily Castle: Yellow guy.
Pac Maze: Too big, pellets are dumb, ghosts are dumb, too big. Also, too big.
Omega stages that I hate:
Brinstar: Ugly, annoying music
Mushroomy Kingdom: Ugly, bad music
Corneria: If it used Brawl's Corneria theme, this would be a high quality stage
Prism Tower: The background hurts my eyes
Mute city: The background hurts my eyes even more
Warioware: Hi camera
Distant Planet: Ugly, bad music
Wily Castle: Annoying
Ya, I hate most stages on this game. Balloon Fight is alright, it's gimmick is so dumb that it's actually kinda funny.