The Pokémon of Super Smash Bros. Ultimate in pictures, according to Poképédia.

The Super Smash Bros. Ultimate logo.
Greninja in Super Smash Bros. Ultimate.
Squirtle, one of the Trainer’s Pokémon.
Charizard, one of the Trainer’s Pokémon.
Incineroar uses Darkest Lariat.
Incineroar uses Cross Chop.
Greninja uses Water Shuriken.
Greninja’s Secret Ninja Attack.
Squirtle uses Waterfall.
Ivysaur uses Vine Whip.
Charizard uses Flare Blitz.
The Trainer’s Pokémon Change.
The Spear Pillar stage.
Bewear coming out of a Poké Ball.
Pyukumuku coming out of a Poké Ball.
Abra coming out of a Poké Ball.
Darkrai coming out of a Master Ball.
Arceus coming out of a Master Ball.