Nuclear Fallout

Each creature gets twice -X/-X until end of turn. Each player gets X rad counters.

Deadly Tempest

Destroy all creatures. Each player loses life equal to the number of creatures they controlled that were destroyed this way.

Flood of Tears

Return all nonland permanents to their owners' hands. If you return four or more nontoken permanents you control this way, you may put a permanent card from your hand onto the battlefield.

Chandra's Ignition

Target creature you control deals damage equal to its power to each other creature and each opponent.

Final Showdown

Spree (Choose one or more additional costs.)
+ {1} — All creatures lose all abilities until end of turn.
+ {1} — Choose a creature you control. It gains indestructible until end of turn.
+ {3}{W}{W} — Destroy all creatures.