"It's best to use Cofagrigus's support early- and mid-game by setting up Trick Room and burning opponents if you opt for it. Take advantage of its bulk by checking threats such as Scizor, Garchomp, Terrakion, Genesect, and Lucario. Attempt to sweep later in the game when Cofagrigus's hard counters are weakened or eliminated. When boosting with Nasty Plot, do not get greedy with it, as one is often enough; boost further only if you are certain that boosting again will not break your sweep."
http://www.smogon.com/forums/threads/cofagrigus.3495517/ 
