089 Muk

Poison Jab is recommended for its STAB damage output and above-average energy generation.

Thunder Punch is Muk's cheapest charge move energy-wise, and provides valuable coverage against common Water and Flying Pokemon. Dark Pulse features a balance between energy cost and damage output, and also provides coverage against Muk's weakness to Psychic-types. Acid Spray provides utility with its guaranteed -2 DEF debuff on the opponent, but it costs less energy to bait shields with Thunder Punch instead. Sludge Wave costs less energy than Gunk Shot if a high damaging charge move is needed, but Poison-type attacks aren't very valuable generally speaking. 

Muk is a mono-Poison type with respectable bulk. Updates to its movepool throughout rebalances in 2019 have improved Muk's performance in the meta, with Thunder Punch being a valuable asset against common Water and Flying picks, while Dark Pulse and Acid Spray provide accessible options compared to Muk's more expensive charge moves. Unfortunately Poison-typing isn't very useful in the meta partly due to the frequency of Steel-types, and Ground-type coverage is quite common among various meta Pokemon. 

As a Poison-type, Muk is mostly a niche pick to counter certain Pokemon like Fairy-types and Virizion. Ubiquitous Steel-types in this league makes it difficult to justify Muk as a pick on the roster, while access to Dark Pulse is inadequate when dealing with bulky Psychic-types. 

With a max CP of 2757, Muk lacks sufficient stats to perform well in Master League.