When you say an employee is terminated, it means you have issued a Termination Letter, mentioning the reason for termination. In such a case, there is no need to issue a separate relieving letter. The Termination Letter itself will state that your services are terminated, and you are relieved on a specific date.
In case you do not wish to issue a termination letter and potentially harm the employee's future, then take them into confidence, obtain their resignation, and issue a formal relieving letter.
A relieving letter includes details such as designation, scale of pay, service period, reason for leaving, etc., whereas a termination letter may not cover all these aspects. What harm is there in issuing a relieving letter when the terminated employee has completed all formalities as per procedures?
Regards,
Pon