I think you should make this end game Alex.. Prototype 2 Alex might be much, but I think Doomslayer has a fair chance against End Game Alex. As it stands Doomslayer wins fairly easily. Yes Alex has a solid stat advantage in most areas, but Doomslayer is tough, like ridiculously tough, and his weapons have the AP to put Alex down. Generally speaking that's what he relies on to win fights anyways, that and maybe mobility, which he's outclassed here in, but he's got options to slow Alex down. I could be wrong in my analysis as it currently stands, but i'd bet on it.
Anyways, great fight. surprised it hasn't been done already