Agatha of the Vile Cauldron has power 1 or greater.
({R} magic symbol) available.
Steps
Give Olivia deathtouch, if needed.
Activate Olivia's first ability by paying ({R} magic symbol) , dealing 1 damage to a creature an opponent controls, destroying it due to Olivia's deathtouch, and putting a +1/+1 counter on Olivia.
When the creature dies, Revel in Riches' first ability triggers, creating a Treasure artifact token.
Activate the Treasure by tapping and sacrificing it, adding ({R} magic symbol) .
Repeat from step 2.
If you have a way to give Olivia deathtouch indefinitely, you may repeat this loop whenever a creature enters the battlefield under an opponent's control.
Results
Destroy all creatures opponents control.
Destroy all creatures that enter the battlefield under an opponent's control.