Hello, just got done doing a playtest with Mazen2892 for Mewtwo.
Mewtwo is a fun but challenging foe. His ability to use the counter to change dice is a great ability for an event hero, while having an appropriate limit to its power. It feels like you have to pull all your team's resources to exhaust the counter so you can put damage on him; exactly how an event hero should feel. I would approve of this design.