Dear Sidharth,
I wish you had provided the proper context for your query. You requested the format of the letter for "retaining a resigned employee" but did not specify who will write the letter, to whom it will be addressed, what the retention benefits are, or whether the resignation was voluntary or involuntary. Without this background information, a draft cannot be provided.
If you provide this information, ChatGPT can readily provide a draft. Of course, you will need to decide what changes to make and where to make them.
Thanks,
Dinesh Divekar