Jarad, Golgari Lich Lord

The Golgari guildmaster's whole design is a closed loop, and a famously brutal one: every creature card in your graveyard makes him bigger, and the sacrifice ability converts a fed creature directly into life loss. That sacrifice clause is the engine that earns his reputation. It does not deal combat damage and it does not care about the board, so it sidesteps blockers, fog effects, and toughness math entirely, pointing the sacrificed creature's power straight at every opponent at once. Feed it something large (a trampler, a token-doubled fatty, a creature pumped before you activate) and it becomes a one-card kill that no amount of life gain quite keeps pace with. The constraint that keeps the loop honest is the word another: the fling demands a second creature as fuel, so Jarad can never eat himself for damage. That restriction is exactly what makes him a permanent piece of the engine rather than a single-use payoff. His third ability completes the picture: sacrifice a Swamp and a Forest and he returns from the graveyard to your hand, meaning even a stocked graveyard can fund his own comeback for the cost of two lands. Die to removal or to attrition, claw back for the cost of two lands, and resume flinging the next body. That self-replacing quality is the difference between a fragile creature that grows and a recurring trigger-puller that keeps converting the graveyard into face damage, which is exactly the loop Golgari wants: nothing is ever really spent, only routed back through the grave and out the other side as life loss.