obsessination
When you're so obsessed with someone you'd rather punch a hole in the wall than let anyone else look at them. They're like a lovesick hyena that wants to rip your throat out if you breathe too loud.
My ex is obsessed with my new girlfriend. He texted me 'I will murder her if she texts me first.'
My sister's crush is so obsessed with his crush that he stalked him to the mall and threatened his best friend.
My dad is obsessed with my mom's best friend. He thinks she's trying to steal her away and he says 'I will kill her if she smiles at him again.'