Shalai and Hallar, and The Red Terror

Prerequisites

• Shalai and Hallar on the battlefield
• The Red Terror on the battlefield
• You have a way to put a +1/+1 counter on a creature you control

Steps

1. Put a +1/+1 counter on a creature you control
2. Shalai and Hallar triggers, dealing 1 damage to an opponent
3. The Red Terror triggers, putting a +1/+1 counter on itself
4. Repeat from step 2

Results

• Infinite +1/+1 counters on The Red Terror
• Infinite damage