Fiendlash, Wrathful Red Dragon, and With Great Power...

Prerequisites

• Fiendlash on the battlefield
• Wrathful Red Dragon on the battlefield
• With Great Power
• on the battlefield

Steps

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

Results

• Infinite damage