Odin.
From some of the stories that Van had heard, he was supposed to be the strongest of all the Aesir; and perhaps even the strongest in all of the 9 Realms. And according to Surtr, he was the oldest breathing Aesir still alive from the Great War that had happened tens of thousands of years ago.
He was the one single-handedly responsible for keeping all the other races in check. Although Van had only heard brief stories about him, he knew that he was feared by even Surtr-- that alone should show the magnitude of Odin's strength.
And now, not even a week after arriving in Asgard, Odin was already right in front of him, in the flesh. Van had even jokingly thought that old man Bjorn looked like someone that would be named Odin, but lo and behold, he was.
