4. Fallout 3/New Vegas/4

As our friend Shadman said, the gore in this game is almost pornographic. Slow motion showing dismembering limbs, exploding heads, grenades sending bodies to fly, lots of female enemies, cannibalism and more. And this is the open world Bethesda game, so there is thousands of mods you can install, and this mods has almost everything you wished for. New Vegas also has very interesting story and quests. And you can play as the bad guy in all of this games.