He/she manipulates you by gaslighting or guilt-tripping.
He/She doesn’t respect your feelings, boundaries etc.
They are very controlling such as they decide what you wear or where you should go and whom you can meet etc.
They don’t support you in your decisions, dreams or future.
Always criticize you negatively like “don’t eat too much you’ll get fat” or belittles you.
If they physically or mentally abuse you privately or publicly.
If your partner doesn’t believe/trust you and is constantly suspicious of you.