BioShock Infinite

If BioShock Infinite has an equivalent to the Big Daddy of past games, then the Handyman is it. It's probably the most difficult foe you'll face, and the human-steampunk-robot hybrid androids keep popping up at the worst times. They have electric and melee attacks, and they can leap fully across most environments. If that's not enough, just wait until you have to fight them alongside a dozen other enemies.