The Rage System was a system that was first introduced in Tekken 6, though a similar system, Netsu Power, had been implemented already in Tekken Tag Tournament. The Rage System activates when a character's health drops below a set point, thereafter the character enters "Rage" and has increased attack power. The set point was initially set to 10%, but after complaints of it being too high, Namco created a patch where the set point was decreased to only 5%. This can be changed in Scenario Campaign.
During Rage, a character's hands and feet will have an afterglow, which reportedly is default red in all characters, but can be customized to appear in other colors. Also in Scenario Campaign mode, how much damage inflicted when in Rage can be modified.