If you look closely, there's a pill in the cave which is suddenly missing (because Alfred ate it). That pill is a kryptonite thingy-majing which confers superpowers and stuff to whoever eats it. It's a plot point of the Injustice game, making the streetlevellers able to go toe-to-toe with the very powerful characters, like superman (although I do think that surprise worked very much in Alfred's favor here).
Alfred was so badass in this! I loved every second of it.