Here's something you can do with Gengar.  If he can knock out the
defending pokemon more than its HP eg: scyther has 20 hp left, curse the
damage to someone on your opponent's bench then use dark mind and do 10
damage to the pokemon you just cursed to.  Voila! 20 damage to a pokemon
on the bench.  If you get really lucky you can get 3 KOs a turn with
Gengar. 1 with dark mind's damage, 1 with curse, and 1 with dark mind's
special effect.

Hope you can use this strategy
By Eggman: e-goblak@home.com