Make Olimar heal the same amount of damage he does in every attack.
Make Donkey Kong able to use Bongo Blast like in DK64, hitting every foe on-screen. (Same goes for Diddy Kong with Guitar Gazump.)
Make Mario able to spin his Cape to stop all attacks and damage enemies, as well as having no lag in between spins.
Make Snake use his ground attacks as aerials.
Make Jigglypuff's Rest have a hitbox the size of Octopus.
Make Captain Falcon's Falcon Punch ten times larger.
Make Samus always have a full charge shot.
Make Kirby's Hammer have no lag.
Make the eggs from Yoshi's Egg Toss home in on you until they hit.
Make Pit's recovery double in distance when hit while using it.
Make Sonic's Homing Attack have infinite range on the homing part.
Make Link have Meta Knight attack speed.
Make Ganondorf's Flame Choke capable of hitting foes on an infinite vertical axis (he jumps to reach anyone above him).
Make Wario's Bite have a suction effect like Kirby's Inhale, except covering all of Temple and having the moving power of FLUDD.