1. When The Genie Fell In Love With Regina
Basically, it's safe to say that falling in love with Regina is a dangerous game. To his credit, the Genie aka Sydney Glass didn't know how evil Regina was when he initially fell in love with her.
But he really should have second guessed her request for him to help her LEGIT MURDER her husband. Because of his love blinders, he murdered a man, got stuck inside of a mirror and then became Regina's puppet in Storybrooke as well.
This dude's one-sided and desperate affection for the Evil Queen is majorly unhealthy, and he really needs to sort out his priorities.