Berserker
The hero can enter into a battle rage that alters the hero in some significant ways. Reason and Psyche plummet to Fb rank while the ranks for Strength and Fighting increase by the same number of ranks. (That is, the total number of points lost are split evenly between the Fighting and Strength ranks.) The hero also develops Iron Will for the duration of the Berserker rage; the rank for this is the same as the Berserker Power's rank. The Berserker lasts for the length of combat and 10 turns. When the rage ends, all the altered Abilities return to their original ranks. Since the Iron Will also disappears, the hero finally feels the effects of any damage he suffered while in the Berserker rage.
Example: Orlando the Furious has Fb Strength, Gd Fighting, Rm Reason, In Psyche and Ex Berserker Power. When he enters the Berserker rage, the following occurs. Psyche and Reason drop to Fb, a total of 66 points. This is between Orlando's Strength and Fighting ranks. Strength increases to Rm, Fighting to In. Finally, he develops Ex Iron Will. The carnage that ensues is short and messy. Orlando emerges victorious but remains rather dangerous to be around for another 10 turns (5 minutes).
The Optional Power is Natural Weaponry. Thus, you can build your own Wolverine (or other violent, crotchety animal from the northwoods).
The Nemesis Power for this is Mind Control.