Well to start with maybe broaden your idea of evil. Just killing and murdering is evil but there are lots of other ways to be evil.
What about slowly turning good characters bad by slowly encouraging them to do small wrongs. Like convincing them to pick someone’s pocket. Or justifying theft and other petty crimes.
What about looking the other way when criminals commit crimes and just saying… Not my problem.
Start thinking about long term goals and then add narcissism and selfishness to every choice.