Fiendlash, Truefire Captain, and With Great Power...

Prerequisites

• Fiendlash on the battlefield
• Truefire Captain on the battlefield
• With Great Power
• on the battlefield

Steps

1. Deal damage to Truefire Captain
2. Truefire Captain and Fiendlash trigger
3. Resolve the Truefire Captain trigger, dealing damage to an applicable target
4. Resolve the Fiendlash trigger, targeting you, but dealing damage to Truefire Captain instead due to With Great Power
5. Repeat from step 2

Results

• Infinite damage to target player