Massacre Girl, Most Wanted, Agatha's Soul Cauldron, and Walking Ballista

Prerequisites

• Massacre Girl, Most Wanted on the battlefield
• Agatha's Soul Cauldron on the battlefield
• Walking Ballista in exile

Steps

1. Activate Massacre Girl using Walking Ballista's ability by removing a +1/+1 counter from it, dealing 1 damage to an opponent
2. Massacre Girl's second ability triggers, putting a +1/+1 counter on it
3. Repeat

Results

• Infinite damage