The evil and wicked like to watch their victims tremble. To watch them shiver and cower. They don't usually kill outright, they revel in their power over the "weak".
That's plenty of time for me to become "the cornered rat who bites back". Granted, it only takes like, 5 seconds to completely shift into the self-preservation state, but still. My instincts are in complete control, and I transcend the average state of fury.
At that point, most higher level conscious thoughts are heavily suppressed; anything that would instigate restraint is forced into "standby mode". All thoughts that would equal "vicious dismemberment" are overclocked at the psychological and physiological level; survival odds are greatly increased if the threat is permanently destroyed, after all.