Deathstroke

At the beginning of the game, secretly choose a
player. When you cause the chosen player to lose
the game, reveal Deathstroke. You win, and
nobody else can win this turn. If someone else
causes the chosen player to lose the game, reveal
Deathstroke. You lose the game.
You may flip this card face up at any time. When you do, prevent all damage that would be dealt to
your chosen player this turn. You may destroy
up to 3 creatures any player besides your chosen
player controls.