Termination without cause and they can claim unemployment. With cause, they have to look for another job.
That’s where the Performance Improvement Program comes in. The HR trick is to make up some deficiency. A claim that people feel threatened by the subject employee. You can make up all sorts of head trips with this. Have him go through an increasing number of management employee “counseling sessions “ where it not only messes with his head, it interferes with his doing his job. Have more hoops that he needs to jump through. Liberal HR departments do this all the time with employees deemed to be a problem even if the employee is a high performer and works well with the team. Except in this case you are cutting dead weight that could be a high liability. Just document everything, be creative, be ruthless.