1. Wheatley Portal 2
Wheatleys betrayal in Portal 2 isn't just shocking but rather hilarious. I've been a long-time fan of the Ricky Gervais Show, so the idea of Stephen Merchant betraying anyone is foreign to me. Glados is back to her old shenanigans, so it seems entirely harmless to put Wheatley in her chair. Whilst at first he seems to be your ally and a lovable idiot, he becomes increasingly erratic and hostile. As soon as he gets a taste of power, then suddenly hes not your best and only friend, hes a crazed little ball with an inferiority complex and power over the entire facility. Whilst Glados was a formidable enemy, she had some reasoning behind her actions, whereas Wheatley becomes one of the most powerful enemies you will ever face in any video game; hes an idiot with power, a lot of it.