now... in a logical world, he would destroy the kingdom.
yea sure there's some "innocent" people living there. but he can just not attack the innocent. maybe destroy the palace and the throne at the very least?
not to mention the princess is already on his side. he can marry her and become the new king and do, arguably, a much better job than the current administration.
i know he won't do all that. worse still, he's probably gonna spare his "brother". but a man can hope.