Corrupt

In Commander, Corrupt is a role-player in dedicated mono-black lifegain or drain builds — the Swamp count scales naturally as games go long, and a seven-mana instant that gains six or seven life while dealing the same damage is a real return on investment. Outside Commander, the calculus gets harsher: Pauper is the only competitive format where Corrupt sees meaningful play, specifically in mono-black control shells that can reliably hit the Swamp count needed to make the drain threatening. In Legacy, Modern, and Pioneer it's legal but outclassed — faster formats don't give you the turns to build a Swamp base, and seven mana buys you game-ending threats instead. Vintage has the same problem at a steeper level.