Term. Contempt — mockery, sarcasm, looking down on a partner.
Why it’s dangerous. Research names contempt the strongest predictor of breakup: it tells the partner “you’re beneath me”. It’s not a conflict on the merits but an attack on dignity.
Antidote. A culture of respect and gratitude: deliberately notice the good, speak of the problem without demeaning the person.
Lesson. You can argue about actions, never look down on the person.
See The Four Horsemen.