That's a good and valid question. I've been thinking about it, and I've come to the conclusion that, yes, it's possible. Because there are resurrection spells of the 3rd and 5th levels (Raise Dead and True Resurrection), so you need to manage to truly resurrect at least one unit before the last hit. I emphasize that the 4th-level resurrection spell will not work for the final resurrection (although it can be widely used during the battle).

Oh, I'll reveal a great secret, although I think it's not news to many. If, at the moment of killing the last enemy unit, you only have a unit resurrected by a regular restoration (4th level) on the battlefield, your hero will not disappear and will remain on the map with 1 unit from that unit.
Well, I've revealed the great secret. By the way, before writing this message, I specifically checked it again, as I have ready-made arenas at hand. I don't know which monster will remain if you have several such units. So, there's no need to build a 5th-level structure, and it also saves mana.

And the technique criticized in the next post is not underhanded at all, but very strategic, especially since running away won't help, as the enemy hero will also end up in the tavern. To eliminate someone else's hero, you need to sacrifice your own. But this is more relevant to online play.