The Stress Flame is the (probably unofficial) name for the flame that occurs when a character's Stress Meter reaches its peak. This blue flame (later purple) bursts forth from around the angered character, surrounding them and providing a moment of invincibility. A hapless opponent who happens to be too close or attacking at the time the stress flame comes out will take a small amount of damage and be sent flying back. Opponents can also be KO'd by this flame.
The Stress Flame would have other properties in later games. In Matrimelee, it would heal anything leftover in the red healing gauge. While games after it would drop the Stress Meter, the Stress Flame remained, occurring every time the bar gained a level. In Goketsuji Ichizoku Matsuri Senzo Kuyou, the stress flame would occur only if the character reached the maximum amount of levels when he or she is hit by an attack.