By default, only community admins are able to delete, suspend, lock,.. a member's account.
If you are an admin, you can delete an account by going to the user's account> Edit Profile> Delete User Permanently> Save.
You can also change the status of an account from "active" to "suspend", "lock", "waiting for approval", ... by going to the user's account> Edit Profile> Change Status> Save.
If you want your regular members to be able to delete their accounts, you as an admin should give them access to do so. Please go to Admin Panel> Settings> Access from top menu> Removing Users should get changed to "Users can delete their own accounts"> Save changes from the bottom-right.