Procedures of terminating an employee for taking unapproved long leave

My employee went on approved annual leave for 2 months in November 2021 and was expected to return to duty by January 2022. But he returned only today after more than 5 months.

As an employer, where do we stand in this matter?

What disciplinary actions can we take against him?

If we decide to terminate his services as a disciplinary action, what are the obligations to us?

Please guide.