Beat Pro on 3rd day (yes i took a weekend to smash it), the U-8 is best beaten with grenades, equip a good shotgun to deal with the bugs fast, use Magnum on the legs and when its down run to its mouth and hit X (so long as you have a grenade in inventory, doesn't need to be equipped) 3-4 times should do it. NOTE: every time you do this he will try to instant kill you with his pincer, soon as you lob that thing in RUN LIKE HELL!