Demons or Devils aren't always portrayed as evil entities in franchises and folklore, as some can be good at heart and fight for justice. These kinds of heroes may be good from the start, or start out evil and then become good due to their backstory or confrontation with other heroes.

In spite of being good guys, they are still dangerous due to their demonic abilities. They could be chaotic due to these as well which means they can be the best allies or friends ever had and the worst enemy possibly imagined. Those who gained demonic powers (e.g. Johnny Blaze) are fair game as well.

Demons can even have a chance to be Pure Goods in some cases since they are willing to be good without despair or any negative traits whatsoever.