As was said earlier, mundane methods are usually best. But fear warding is pretty effective.
A spell that makes it so that anybody intending to do harm is afflicted with a deep sense of fear,, hesitation, etc. can go a long way toward avoiding conflict.
A spirit companion can also be a potent source of this fear or intimidation.
You can also make it to varying degrees, utilizing negative energy. Should the threat level increase it can make them physically tremble, sweat, get nauseous, dizzy, tired, etc.
Symptoms that will fade as the threat withdraws.