They Feel No Guilt or Remorse
If your partner is a psychopath, they may hurt you either physically and verbally. However, they don’t feel bad for hurting you or anyone for that matter. They have no remorse for their actions and they will manage to blame you for what they've done and make you feel bad for saying anything at all. They do not respect your feelings and what you need in a relationship.
If you caught your partner cheating, a psychopath may promise that it was a one-time thing and will never happen again. Despite this, no matter what they say it always seems to happen again and again. They continually make choices that hurt you without showing the slightest amount of care. This is their way of manipulating you. The only thing they are sorry about is being caught.