I would like to delete all my data and my user from macbook pro before returning to ex, who is administrator. is this possible?

You need to perform all but the last step in the Apple article @BobTheFisherman provided so that you don't leave your AppleID or other accounts linked to this Mac.

To delete a macOS user account, you need to do so from another admin user account. If you do not have an admin user account or access to another admin user account, then you will need to have your ex delete your user account for you. Here is an Apple article:

Delete a user or group on Mac - Apple Support

Follow these instructions: What to do before you sell, give away, or trade in your Mac - Apple Support

Balloons77 wrote:

Can I remove my own user and data from my MacBook Pro without being the administrator?

For your user account—

Erase all content and settings on Mac - Apple Support