Toxicroak

Toxicroak isn't a bad attacker, but when face-to-face with the stronger options in any niche that it can occupy, Toxicroak croaks.

Best PvE Offensive Moveset

• Counter and Dynamic Punch make Toxicroak a decent Fighting attacker.
• Pair Poison Jab with Sludge Bomb for great Poison-type DPS.
• Mud Shot and Mud Bomb can work if you're absolutely desperate for some Ground Type damage, but it's severely outclassed.
• Shadow Ball doesn’t have any offensive use for Toxicroak.

Best PvE Defensive Moveset

• Poison Jab and Counter perform very similarly on defense, but Poison Jab has wider type coverage.

• Same thing goes for Sludge Bomb and Dynamic Punch.

• Mud Bomb has lower energy cost, but it’s very weak and easier to dodge.
• Mud Shot is poor on defense.
• Shadow Ball hits pretty hard and has great counter-coverage, but Toxicroak is likely to drop to a few Confusions regardless.

Counter is the go to fast move for Toxicroak as it provides wide coverage and gains STAB. 

Mud Bomb provides wide coverage and costs the least amount of energy. Sludge Bomb costs a modest amount of energy and provides situational coverage while benefiting from STAB. Shadow Ball can smack Psychic- and Ghost-type Pokemon that would otherwise be problematic for Toxicroak. Dynamic Punch, 90 Damage and 50 Energy cost, is also an option to double down on the Fighting coverage depending on the PvP format.