It is important to understand the difference between real repentance OR remorse when making decisions about the future of a relationship. Abusive people control others in various ways. Victims live in fear of their partners unpredictable angry outbursts which often is influenced by alcohol.
Remorse occurs as a result of a very selfish focus that is more concerned about being released from the intense feelings of self condemnation than really caring about the people they have mistreated.
When an abuser feels that they have gone too far with volatile/dangerous behaviour they can feel intensely bad. This feeling of badness and regret can create very strong self condemnation and shame. Whilst feeling bad the first impulse is to reduce self condemnation by being remorseful, offering extensive apologies or promises that it will never happen again.
But even with copious promises to change that it will never happen again the change is only temporary. And the next time they go too far with controlling or aggressive behaviour the same cycle of remorse is repeated with no actual permanent change in behaviour or attitude over time. This cycle will be magnified when alcohol is involved, escalating abusive or threatening and dangerous behaviour. People in an abusive relationship can spend much of their life tiptoeing around the emotions of their abusive partner.
Repentance is different to remorse. When your partner is repentant for their poor or emotionally dangerous behaviour there will be an apology and a general sustained change in behaviour.
Repentance is possible for those who can be empathically caring for the needs of another and genuinely see that they have caused harm. Repentance involves admitting and taking responsibility for the poor behaviour which is accompanied by a request to be forgiven and behavioural change. Repentance occurs in the process of self reflection and self evaluation that causes the cessation of a behaviour that is personally and relationally unhelpful.
The key identifier is that if changes does not last and you continue to live in fear it is more likely to be remorse than repentance. While you are addicted to hope in the promise of change, the promise to change is a manipulation to control a partner from leaving an abusive relationship.