The first encounter with the hulking Big Daddies in the original BioShock was, without a doubt, one of the most terrifying moments in modern gaming; but, eventually, you figured out that these huge dudes in old-school diving gear that scream and run at you with giant drill bits aren't quite as invincible as you thought - still pretty tough, but not unkillable. BioShock 2 sees you return to the underwater setting of Rapture, this time as a different conflicted protagonist, and this time with a different set of challenges to contend with. The Big Daddies were terrifying in the way that having Andre The Giant sit on you would be terrifying - they can crush you like a bug, and they've got terrifyingly deep voices. The Big Sisters, meanwhile, are more lithe, always seem to be angry, and so are a constant danger. Especially the first one you encounter after booting up the game, who you can't actually defeat...