Delete a commit remotely after the source branch was deleted

Hello everyone, Accidentally I commited an file that I shouldn’t, I removed the source branch remotely and locally as well, I thought the commit was deleted with the branch.
The problem was when I saw that I had a merge request closed and there were still the commits from the branch that I had already deleted, I wasn’t able to find how to delete the merge request or remove the commit from history since they don’t have a branch.

Do you guys know what could I do? I already used git prune and git gc to remove unaccesable files, but the commit is still able to be accessed using the hash.