100% Max Power is a form a Saiyan transformation when used by a Changeling. The user pushes their power output to the limit, bulking themselves up like a Super Saiyan Second Grade at the expense of speed.
Unlike the typical Changeling transformations, 100% Max Power doesn't change the way the Changeling looks. Instead their muscles just balloon to crazy proportions as well as their veins popping out of their skin.
Iced uses this form against Vegeta.