Bad Temper is one of Fallout GURPS disadvantages. See: Fallout GURPS.
You are not in full control of your emotions. In any stressful situation, you must make a Will roll. A failed roll means you lose your temper, and must insult, attack or otherwise act against the cause of the stress.”— Steve Jackson Games GURPS sources
With the abandonment of GURPS, Bad Temper was removed from the game