Massacre Wurm

When this creature enters, creatures your opponents control get -2/-2 until end of turn.
Whenever a creature an opponent controls dies, that player loses 2 life.

Overwhelming Forces

Destroy all creatures target opponent controls. Draw a card for each creature destroyed this way.

Harvester of Souls

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
Whenever another nontoken creature dies, you may draw a card.

Dread Cacodemon

When Dread Cacodemon enters, if you cast it from your hand, destroy all creatures your opponents control, then tap all other creatures you control.

Soul Shatter

Each opponent sacrifices a creature or planeswalker with the highest mana value among creatures and planeswalkers they control.

Chevill, Bane of Monsters

Deathtouch
At the beginning of your upkeep, if your opponents control no permanents with bounty counters on them, put a bounty counter on target creature or planeswalker an opponent controls.
Whenever a permanent an opponent controls with a bounty counter on it dies, you gain 3 life and draw a card.

In Garruk's Wake

Destroy all creatures you don't control and all planeswalkers you don't control.

Vraska, the Silencer

Deathtouch
Whenever a nontoken creature an opponent controls dies, you may pay {1}. If you do, return that card to the battlefield tapped under your control. It's a Treasure artifact with "{T}, Sacrifice this artifact: Add one mana of any color," and it loses all other card types.

Revel in Riches

Whenever a creature an opponent controls dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
At the beginning of your upkeep, if you control ten or more Treasures, you win the game.