People are saying you're going to be fighting him directly. It's ridiculous. The link corresponds with the text I posted, you are not going to punch out cthulhu.
And we already know why he stopped before. Marukh and his selectives shaped him into akatosh, removing his more destructive tendencies. Since the covenant is broken, he reverted to Alduin/Auri-el.
Further Edit: Yes he is that huge. Can eat the world implies larger than the world. And you're completely off on the mythology remark. Take a look into the lore forum.
I gotcha now. Just wondering whether or not you were criticizing that style or not.
Also, as far as the base lore regarding Alduin, his complete story is not fully detailed aside from those basics. I am specifically referencing the Game Informer article detailing the description of Alduin's Wall, and how one of the concerns of the PC during the MQ will be discovering exactly how the 3 characters present on the wall "defeating" Alduin come into play. Todd himself mentioned as well that a key to the MQ will be learning that full story. I think of it in a similar vein to the role of the Mythic Dawn and how the PC has to address them and Mankar Camoran in OB to have "the keys" to defeating Mehrunes Dagon.
And yes, you are right to point out the obvious: If the enemy is bigger than the world, you'll need something bigger/better than a sword to beat it. However, until the game's story unfolds for us all, it remains to be seen exactly how we will defeat Alduin. I place my bets on it being somewhat surprising though, knowing Bethesda.