Learner accounts/profiles cannot be deleted. However, you can use the Account Merge Tool to merge unwanted accounts into a "trashcan" account. The "trashcan" account is simply a fake learner account you can create that is used only for merging unwanted accounts.
If you are going to use the merge tool for this purpose, be sure to first delete all participation records (if there are any) from the unwanted accounts before merging accounts into the "trashcan" account.
