It depends on which one is the final boss. If it's the one with a bunch of paladins, I barely managed to kill him. This hero had a weakness. With 170 mana, he would immediately start using it to cast antimagic on all creatures one by one. As a result, during the battle with an empty hero, he would waste 28 mana units. So, it was enough to send 6 empty heroes against him, and his mana would run out. There were about 600 skeletons. There was a 4th-level resurrection spell (not true resurrection), so I simply resurrected 1 champion rider with it and attacked the blinded enemy once. Of course, he was killed, but at least 600 skeletons could unleash their attacks without any consequences. It was impossible to shoot down such an army with archers because there was no artifact of infinite arrows.

If it's the one with a bunch of thieves, archers, and 6000 peasants, then I easily defeated him because I had about 1000 skeletons and a paralyzer.