0094 Gengar

Shadow Claw is the superior fast move in both damage output and energy generation. Don't use any other fast move.

Shadow Punch is a charge move limited to Community Day or Elite TMs, but is essential for baiting shields due its low 35 energy cost. Shadow Ball is Gengar's most efficient charge move in terms of Damage Per Energy (DPE), has incredibly high damage output with STAB and Gengar's high ATK stat, and hits most Pokemon for neutral damage. Focus Blast can be chosen as an option to fight against Dark and Normal-type Pokemon meant to counter Gengar, but its high energy cost makes it difficult to access. Sludge Bomb is generally not recommended, but can still be useful in certain formats to threaten Fairy-type Pokemon. 

Gastly Community Day allows Gengar to perform very similarly to the scary Haunter, with identical movesets (and additional options for Gengar) and similar bulk. High offensive threat and very vulnerable fragility still causes Gengar to demand shields to perform most optimally, with very scary potential to play bait-and-nuke tactics against Pokemon that can't eliminate Gengar quickly. The differences between Haunter and Gengar are minor, though Gengar's slightly higher bulk trades certain matchups for others due to less damage output. 

The very scary and threatening Haunter-style of play seen in Great League can now be utilized in Ultra League with Gengar. Bait-and-nuke plays can easily deal with a majority of the meta, though this can be risky and Gengar can fall behind if played incorrectly or if shield baiting is unsuccessful. Giratina's high bulk still can give Gengar trouble, with difficulties against Shadow Claw Giratina due to its faster energy generation. As a Ghost-type, Gengar can struggle significantly to fight bulky Psychic-types in this league due to its Poison sub-typing, with considerable losses against Pokemon using Confusion when shields are in play. 

Gengar has a max CP of 2878, which is considerably less compared to the numerous legendary and pseudo-legendary Pokemon found in this league. Many Pokemon can beat Gengar through superior stats or efficient movesets, which makes Gengar less appealing to use. Mega Gengar when?