Kokusho, the Evening Star

The death trigger is what makes this Dragon dangerous, because it cannot be answered by simply killing it. Most removal trades down against Kokusho: a kill spell, a chump block, even a sacrifice for value all flip a life swing in the controller's favor (five drained from each opponent, and that total life gained back). Against a single opponent that is a Drain Life stapled to a 5/5 flier that demands the spell anyway, and in a multiplayer pod the math compounds with every additional player, which is why the card's most infamous home is the recursion loop: a sacrifice outlet and a reanimation effect turn one Dragon into an arbitrarily large life-drain engine. That loop is precisely what got it banned from Commander for years before a reprint and a softening of the format's attitude brought it back. The design tension here is that the body is almost incidental; a 5/5 flier for six is a fine clock, but the value is loaded entirely onto the moment it dies, inverting the usual relationship where you want your threats to survive. Wizards has circled this space repeatedly since (Sheoldred, Whispering One and the broader reanimation-payoff line owe it a debt), but few death triggers have ever been this clean, this color-aligned, or this punishing to interact with.