Toxicroak
- STAB attacks super effective against Milo's, Opal's, Melony's, Piers', and part of Raihan's Gym, plus various Pokemon in the Champion Cup, and Chairman Rose
- Resists the STAB attacks of Milo and Piers, and is immune to Nessa's STAB moves
- Excellent Attack stat
- Decent Speed
- Can learn moves like Thunder Punch, Ice Punch, Drain Punch, Poison Jab, etc.
- Can be obtained early as a Croagunk, but it'll take a while to evolve it
- Sub-par HP and defenses
- Can't get many good moves from levelling up (best attacks it gets from levelling up are Sucker Punch and Poison Jab)
Galarian Rapidash
- STAB attacks super effective against Piers' and part of Raihan's Gym, plus various Pokemon in the Champion Cup, and Eternatus
- Is immune to some of Raihan's STAB attacks
- Wonderful Speed
- Slightly worse Attack than Toxicroak
- Can learn moves like Play Rough, High Horsepower, Megahorn, Zen Headbutt, Wild Charge, etc.
- Can be captured in Glimwood Tangle, more than halfway through the game
- The only decent moves it gets via levelling up are Quick Attack, Take Down, and Megahorn
- Fairly low HP and defenses
- Evolves pretty late
It depends on the rest of your team, but either works quite well. I'll give a moveset for both.
Toxicroak @ Black Sludge / Black Belt
Ability: Dry Skin
- Poison Jab
- Brick Break / Drain Punch
- Earthquake
- Stone Edge / Thunder Punch
Rapidash-G @ Pixie Plate / Twisted Spoon
Ability: Pastel Veil
- Play Rough
- Zen Headbutt
- High Horsepower
- Wild Charge
Hope I helped!
