Batman has all his weapons??
I'm by no means a big fan of his but he is portrayed as being a very very skilled guy. Of course he falls short in the strength and endurance categories, but by giving him access to all his weapons (he always has something effective on him, no matter how ludicrus) then im sure he will be able to come up with an effective attack on Karnak.
And he is a skilled martial artist and acrobatist, so he would no doubt be able to put up a decenty fight nonetheless .