Christina Schofield (SPOILERS)
It's hilarious that all throughout Seasons 1-4 Michael and Lincoln talk about their mum as if she's some great person, then when they finally meet her she's a cold-hearted b%@#h. Just goes to show that you shouldn't make judgements about someone you don't even know whether it's good or bad.
Also, when Christina told Michael that Lincoln wasn't his real brother, that he was adopted, it was a lie, apparently on the DVD commentary the makers of this series said that Lincoln IS in fact Michael's real brother, Christina said he wasn't simply to play mind games and to confuse Michael.