Sometimes destructive thoughts enter the mind, causing us to wonder if we are capable of harming others, either as an uncontrolled response because of some internal driver or deficit or because we become so single-mindedly obsessed about something (a goal, success, power, etc.) we will do whatever it takes to possess it. For most, these thoughts are fleeting, because common sense prevails—I am moral and have good judgment. For others, though, it becomes a deeply embedded fear: I will harm someone if I don't safeguard against it.

This fear can play out well in storytelling for characters who are unsure where their moral line is or worry they will lose control of themselves. It can also be a good fear for a villain if you wish to hint at their humanity and whether they might be self-aware enough to be redeemed. Characters with Harm OCD may be especially susceptible to this fear.

The character being afraid of their own anger
Warning people away and discouraging relationships
Not liking to be surprised
Intrusive, irrational thoughts about harming others
Compulsively seeking to push an irrational thought of harm away (for example, repeating, "I'm a good person. I wouldn't do that," several times)
Visible shaking
Panicked breathing
Dropping or moving away from the item that triggers ideas of harm
Keeping people at a physical distance
Having only a few close friends or family members