Pokemon Trainer is interesting in that each character has different strengths and weaknesses that drastically effects their match ups, but here's a quick rundown on each monster.
- Good combo game and aerial acceleration, but very short reach and slow Smash attacks. He sometimes has a hard time getting in on characters who can outrange him, just watch out for Withdraw. He's extremely light so it's also possible to kill him early with a hard read.
- Good disjoints and a solid projectile with razor leaf, Ivysaur's attacks can sometimes be a tiny bit on the slow side, especially that grab. If you're able to stay in Ivysaur's face and refuse to let them play their spacing game against you then they will struggle. Shielding can be effective because of that slow grab.
- Your typical superheavy, but with extra mobility to keep up the offensive pressure. Stay calm and don't let Charizard's powerful attacks scare you so you don't make any major mistakes that could lead to an early kill. Like Ivysaur, Charizard doesn't like characters who can get in his face, but he also doesn't like zoners who can wall him out with projectiles since his large body makes it hard for him to jump over them. Don't be overaggressive edgeguarding him either or he might hit you with a Flare Blitz on the way back.
If you want a counterpick, characters who are versatile will flexible playstyles will be most effective. It's important to adapt to the strengths and weaknesses of the pokemon you're fighting and never get to comfortable over relying on the same tactic.