In fiction it seems to be really easy to become a fallen angel. Step one defy God. Step two fall to earth. If I were going to make a fallen angel character, I would make it hard to fall.
To fall you must make yourself a creature of hate. Tear off the wings. A symbol of heaven, where the wings were, replace with spears, barbs, claws and spikes. Remove the soft hands, Hands that can do so much good. Fix swords and daggers to the stump ends. and Finally the words that can uplift, inspire and empower need to be purged. Remove the jaw and tongue. Make every breath a painful affirmation of the deed.
Now that’s a fallen angel.
I bet he drools…Gross.