Recommend doing this against a 2nd controller. Can simply login into another account or hit B at the sign in screen and chose the option to continue without saving.
To use the Mind control move Grodd must use his Character Power. The 2nd Meter next to the burn meter ( under the logo of his head) must be full. When it is full hit
to activate character powers. Then use the Mind control move (Down, Back
The meter will regenerate over time if you happen to get Flash to low in health but your Character meter is not charged.