Avoid people who: 1. Mess with your head. 2. Intentionally and repeatedly do and say things that they know upset you. 3. Expect you to prioritize them but refuse to prioritize you. 4. Can't and won't apologise sincerely. 5. Act like the victim when confronted with their abusive behaviour.
Don't be fooled between character and an act. A person who is truly good-hearted will be kind to everyone, not just the people they stand to gain something from. A person who is truly kind will feel remorse for causing pain, and they will try to make it right.