0454 Toxicroak

Counter, 4.00 DPT (Damage Per Turn) and 3.50 EPT (Energy Per Turn), 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. Dynamic Punch, 90 Damage and 50 Energy cost, is also an option to double down on the Fighting coverage depending on the PvP format. 

Toxicroak sports a unique Fighting/Poison typing, with below-average bulk, and excellent meta-relevant coverage. Its unique defensive typing gives it some valuable niches, especially in Silph Arena Cups, being able to resist Fighting-type damage, and boasting advantages over other Poison-type Pokemon with access to Mud Bomb. Comfortable wins over popular "Steel Tanks" and most Grass-types gives Toxicroak a role that is difficult to replace by other Pokemon. Difficulties with popular Flying-types, Psychic-types, and "mud bois" makes Toxicroak somewhat challenging to use, in addition to Fairy-types when shields are available. Overall Toxicroak is still a very solid Pokemon in the meta, and largely demands player skill and experience to perform well. 

Toxicroak still is a big threat in the Ultra League. Positive matchups against a variety of Pokemon in this league, most notably Steel-types, makes Toxicroak quite versatile. Psychic-types, Giratina, and Swampert are the biggest concern for Toxicroak, while its matchups against Fairy-types are entirely depending on successfully landing Sludge Bomb. 

While he still can be used for the Master League, we wouldn't recommend it. He doesn't have the raw stats or combat power to make a dent into the meta.