Impossible. They're not even from the same universe, let alone era. The only way the two could ever meet is through some sort of universe shift, which would probably destroy the both of them.
Also, Batman. And then Spiderman.
Link
Undeniable proof that Batman is distantly related to the Assassins Creed universe.
seriously...now that's proof...if ever there was one
Actually,i forgot,there was one person who beat BatMan...
Bane.
He broke Batman's back.
To be fair as much as I love Bane, he had Batman level planning and all the intel on Batman while Batman didn't even know he existed. And since then he's been nerfed completely intelligence wise.
And he later got taken down by another Batman. I think it was Jean Paul Valley but it has been a while since I read Knightfall >_>.