I have two sims living in the same house and they hate eachother. I keep trying to repair their relationship with positive interactions, but every single interaction causes a negative impact. They used to be really good friends, but now they're on the verge of enemies.
Sim 1: Evil, Genius, Charismatic, Lucky, and Vegetarian traits. Gemini. Scorpio. Evil-Supervillain job.
Sim 2: Absent-Minded, Hydrophobic, Frugal, Childish, Friendly traits. Hit-Movie Composer job.
I've also got NRaaS installed, if that affects relationships somehow. They are in separate romantic relationships so it's nothing like that.