An incubus OC is practically built for antihero work if you do the backstory right. The trick is avoiding making them just a sad boy with trauma, you know? Like, the classic 'I was abused and now I'm dark and brooding' feels shallow. What if instead, his origin is tied to a broken pact? Imagine a summoning gone wrong centuries ago, leaving him bound to a mortal bloodline not as a master, but as a cursed protector. He's forced to feed on the life force of the family's enemies to survive, which he hates, but the alternative is watching the innocents in the line die because his existence is mystically leashed to theirs. He's not evil, but his survival necessitates acts that look monstrous. That constant, grimy moral compromise—saving someone by damning yourself a little more each time—that's where the antihero tension lives. It's less about wanting to be good and failing, and more about being stuck in a system where 'good' is a luxury you can't afford.
You could also flip the 'seduction as power' trope on its head. Maybe he was created not as a predator, but as a consort for a lonely goddess, a being meant to understand and soothe celestial loneliness. When she faded or was forgotten, he was cast adrift, his purpose warped. Now his innate empathy and ability to connect are his greatest curses; he feels the emptiness and pain of mortals too acutely, and his feeding is a twisted form of palliative care that leaves him addicted to their fading warmth. He helps people, but in the process, he unavoidably harms them and himself. That deep, tragic contradiction between intent and outcome makes him compelling. You're never sure if he's a monster with a heart or a heart trapped in a monster's lifecycle.