Tephraderm + Hive Mind + Star of Extinction + Dictate of the Twin Gods

Tephraderm

Hive Mind

Star of Extinction

Dictate of the Twin Gods

How it works

1. Give Tephraderm indestructible, if needed.
2. Cast Star of Extinction by paying 5.
3. Hive Mind triggers, causing each opponent to copy Star of Extinction.
4. Resolve an opponent's Star of Extinction, destroying a land and dealing 40 damage to each creature and planeswalker due to Dictate of the Twin Gods.
5. Tephraderm's second ability triggers, dealing 80 damage to the opponent who controlled the Star of Extinction copy due to Dictate of the Twin Gods.
6. Repeat from step 4 for each remaining Star of Extinction, including your own if one or more opponents survive.