Randall vs Mike would've been the easy choice, but after some thinking, i chose Drago vs Stoick. While the other conflicts have their own merits, the conflict between Drago and Stoick holds a deep symbolism of Hickupp growing up from a simple smart guy to a leader, and also shows that some people (like Drago) can't be negotiate with. I also believe to this very day that Hickupp lost the wrong parent, which makes the aforementioned conflict hit close to home. The other conflicts may be fun to a degree. This conflict was something that feels like a common conflict among the audience too, because many of us lose people during our lives and we can't control it.