I know I main him and all and have a little bit of a bias, but I'm so surprised at the lack of
discussion. Such an interesting character, and a variety of ways to play him:
Koopa kart: Either use it to approach, to set up combos, or to get characters offstage with its stopping hit.
Abandon Ship (up+b): Great kill move on its own, can be used as falling delay, setup for hammer swing, great for spacing
Mechakoopa: Some are using it for stage control, which is great
when used unpredictably. Can also be used as a projectile. Use in the air as a slight falling delay, or off the stage for gimping.
Dash attack is solid and has priority, grab game is okay at worst (Dthrow for racking it up), pummel game is entertaining because bop, cannonball is a decent stopper and edgeguarding tool.
Recovery game is ON FLEEEK, and well paired with aerial edgeguarding game.
Speaking of his aerials, Fair stays out forever, as does Dair, which has a great autocancel when it hits on the ground, leading to a nice Dtilt, Bair has decent knockback, and Uair is also a decent kill move.
Ftilt has long range, is quick, and has nice knockback. Dtilt has great range, priority, and stays out for a while. Great for blocking approaches. Utilt can set up into a Usmash combo.
Fsmash is unwieldy but racks up damage and kills at pretty low %, Usmash has nice priority and also kills, Dmash is also unwieldy, but is a killer when it lands.
Think I covered everything. Someone push back now pls.