If you ever need to delete a user from your account, doing so is easy.
1) Hover over your name in the top right of any screen.
2) Click “Settings.”
3) Select "People" in the left pane.
4) Click "Delete" beside the user that needs to be deleted, and then confirm on the next screen.
When a user is deleted, the account owner is the only one who can see the leads previously associated with that user—as long as no one else had permissions to those leads. The account owner can then go and reassign those leads as needed.
If there are tasks assigned to a deleted user, assignment is removed from those tasks so that everyone can see them. The account owner can also reassign these tasks as needed.