Gengar

Gengar is a threatening offensive Pokemon thanks to its great offensive typing, stats, and movepool. Unlike most other Ghost-types, Gengar is hard to reliably Pursuit trap thanks to Substitute, which eases prediction and can put the opposing team in a very tough spot. Gengar is also capable of pressuring Fairy-, Fighting-, and Psychic-types like Mega Altaria, Terrakion, and Celebi, which makes it useful for an offensive team to have. However, Gengar has poor all-around bulk, making it very susceptible to faster threats and priority. Its typing doesn't grant it many useful resistances either, meaning it generally has a hard time finding free turns to set up a Substitute. Substitute also often puts it in range of priority and faster threats, making it somewhat easily revenge killed.