It depends! It depends on you how much tolerant you are? How much you are ready to move on and restart again with your partner? How much patience you have to wait for that person to change? How much emotional or rational you are?
First is to understand oneself and then coming to a decision is for me a better approach.
It depends on many factors. Some crimes are so bad that you can't RISK a second chance. Legitimately bad people to exist in this world and even if they do change, sometimes you just have to leave them behind. It is up to the offender to own up and apologise and show they regret their mistake before you should even CONSIDER giving them a second chance. If they show no signs if changing, it is safest and more efficient to leave them be and move on. In some workplaces, employees are required to live up to certain standards, no exceptions and this is often for the good of the company. If someone screws up and puts important things at risk, it might be necessary to fire them. They signed up for the job, they knew what they were in for. Often it is too risky and you shouldn't always go out of your way just for one person. It is their responsibility to move on from there. That is simply how things work.