Depopulate

Each player who controls a creature with power 4 or greater draws a card. Then destroy all creatures.

Each player who controls the most creatures investigates. Then destroy all creatures. (To investigate, create a Clue token. It's an artifact with ", Sacrifice this token: Draw a card.")

Each player chooses a creature they control. Destroy the rest.

Flashback (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Destroy all creatures with power 3 or greater. Then create a Food token for each creature you control. (It's an artifact with ", , Sacrifice this token: You gain 3 life.")

Each player chooses a creature type. Destroy all creatures that aren't of a type chosen this way. They can't be regenerated.

For each player, choose friend or foe. Each friend puts a +1/+1 counter on each creature they control. Each foe chooses one untapped creature they control, then taps the rest.