Who: League Administrator
From User Home Page go to Manage League > Modify League Settings
On the Teams page, teams can only be deleted from a Season if they are not scheduled for any game in that season. League Administrators have check boxes next to such teams, and they can select multiple teams to delete with a single click.
Selecting this option gives Match Secretaries the same ability. If not selecteed, they can only delete such teams one at a time.