>>53416163Pretty much everything. I would say Squirrap and Maymay are the only things that truly don't hold up in the long run and they're still good in early game.
If you just want what's considered best and don't feel like experimenting, spoilers ahead:
Kengeon is the regional bird, has solid overall stats, bulky with decent power and speed and has the possibility of Gale Wings on evolutions.
Semdrop evolves into what many consider the singular best tank in the entire game.
Nauseon has a split evo depending on its higher stat - the Special Attack one is very versatile, has a great type, and terrific stats.
Curicrawl's evo line becomes hilariously broken by late game thanks to Prankster and having a bunch of great buff moves and Baton Pass.
Larvades is considered great by pretty much anyone who's ever used it. Not only is its mid evo super powerful for early game and quick to get its final evo is a top tier electric type. You can also delay its final evolution until 99 for Tail Glow, if you want to wait for postgame and exp grinding there.
Birdhouse is considered probably the most powerful early game mon and will obliterate pretty much everything until the 3rd gym, but even then remains solid throughout the rest.
Finally, even though you have a grass type already, both of Clovour's evolutions are amazing. Though to get the really broken one you will need to keep it as Clovour until you reach the 8th gym.