Warhammer Age of Sigmar: Storm Ground

This is really easy, because you can set the AI's army to be just the hero. Go to Multiplayer from the main menu. Click to change to vs. AI mode. Leave your army as it is, and remove all units except the hero from the opponent's. Choose a deathmatch mode, and when the battle starts, hold back and build up your army. Once you have a few units, engage the enemy hero with them and tear the hero apart. Easy Win.