Exsanguinate

Each opponent loses X life. You gain life equal to the life lost this way.

Platinum Angel

Flying
You can't lose the game and your opponents can't win the game.

Repay in Kind

Each player's life total becomes the lowest life total among all players.

Teval, Arbiter of Virtue

Flying, lifelink
Spells you cast have delve. (Each card you exile from your graveyard while casting those spells pays for {1}.)
Whenever you cast a spell, you lose life equal to its mana value.

Profane Transfusion

Two target players exchange life totals. You create an X/X colorless Horror artifact creature token, where X is the difference between those players' life totals.