It looked like a lost cause but Irvine and that Kushan outcast took down a lot of them in such a short time. By killing all the generals in the battlefield and disorienting the war elephants present that quickly, it looked like they're just dying and destroying themselves without any reason.
I've never seen that much heads ripped off by arrow shots or all of the 5-shots being a headshot that hit various parts in creatively brutal ways. That bow and eyeball sure is something to be that powerful.