One must be careful when dealing with bad people.

Alternative form of better the devil you know than the devil you don't know

Seek to dispel ill-will before a day’s end, and not to act upon desires for vengeance.

The character or person of a devil or Satan.

plural of devilship

In manner, like the devil; characterised or marked by devilry; (by extension) causing mischief or trouble; problematic