You want to know your foes are dead. You go for killing blows when possible, put an extra shot in the corpses to make sure, attack guards you could have avoided, and so forth. A Moderate Willpower check is required simply to accept a surrender or take a prisoner under orders. Even in non-combat situations, you never forget who your enemies are. While this seems like an evil trait, it is not inherently evil, though Dark Side Points will tend to come with it. Animosity is limited to valid targets, not your average joe. An ordinary bar brawl will only elicit use of fists like everyone else. Nonetheless, it is a difficult trait to control for a heroic character.