if you want to go "an eye for an eye" then shouldn't you go massacre and enslave them? that's what they did to the elves.
you should just have killed the king and forced his successor to pay a massive ransom as well as sign a peace treaty that would recognize the elf village as it's own domain and that the human kings would never invade it again.
Carrying a boulder the size of a small hill and tossing it through several layers of castle walls like it's a bowling ball. The very definition of brute strength. And the cherry on top, he reduced the capital to ruins just for making an example. I fear for any future foe if he decides to be serious.