lol you fuckin noob. why didnt you try taking cover or something or running into the castle itself then throwing grenades? i remember now i didnt nuke it, but launched a couple missiles at it, then ran into the castle and basically it couldnt get to me, in this game you're invincible if you walk to an area where a melee enemy cant path to, they just end up running back and forth, and i could just step out and throw grenades every time it did its acid thing. acid thing > peek around corner and grenade >acid thing >turn around corner and grenade
so easy