Week 1 - Edward. He was completely out of his depth trying to handle that sort of task, and just couldn't give Lord Sugar a straight answer to anything in the boardroom. And I think what really sealed his fate was not bringing back Alex when Sugar and both advisers were clearly out for his blood.
Week 2 - Alex. Neither Leon nor Glenn were overwhelmingly at fault in the task, and Alex failed to see what a narrow escape he had the previous week; there were no excuses for slipping into the background again.
Week 3 - Gavin. Decent on the first two tasks, but just completely fell apart leading this one.
Week 4 - Felicity. While Ellie and Natasha were ineffective on the day, Felicity's bad choice of location and her completely misjudging the product mix and sales strategy meant they were realistically dead and buried before they ever set foot in the Bullring.
Week 5 - Vincent. For the simple reason that he ran with an idea that a vet had specifically told them not to use, then failed to bring back Jim, who came up with that idea. I actually don't think Ellie deserved to be fired, as Vincent was assigned the project manager's role by Sugar and showed absolutely no interest in listening to anyone who's name wasn't Jim, but I'd have forced her to be project manager on the next task and finally put her money where her mouth was.
Week 6 - Edna. I'm barely leaning toward her over Zoe, who messed up horribly on the first day of the task. However, Zoe for me at least made a valiant effort to get the team back on track, whereas Edna took a backseat, and had never really shown anything impressive on the previous tasks.
Week 7 - Jim. The last couple of weeks had just been awful for him, and he completely blew the negotiations with the largest advertising agency. Personally, I think Glenn's firing is up there with Karen and Miriam as to one of the absolute least deserved ever.
Week 8 - Leon. This is actually because of something that didn't make the final edit - namely the fact that he worked for the UK branch of that French department store chain, yet "forgot" to relay any useful information to Tom. Aside from that, he sold virtually nothing and barely contributed anything to the task.
Week 9 - Zoe and Tom. When we're talking about such a colossal failure of a task, I think at least two heads need to roll; Zoe deserved to go because she clearly thought she could let Tom and/or Melody take the fall if the task failed, but Tom also deserved to go because he had a good idea with their biscuit but completely screwed up the execution.
Week 10 - Melody. This is another of those occasions when the person who really deserved to be fired was the project manager of the winning team. On the losing team however, Tom was the only one who understood the task, Helen was never going to be fired after her role in two colossal victories, and Melody just didn't get the task and still showed an unwillingness to learn her mistakes (or heck, even admit she was wrong in the first place).
Week 11 - Jim. Honestly, I can't think of a single good decision he made on this task. Natasha wasn't a brilliant candidate by any means, and certainly wouldn't have won, but I somehow get the feeling that Sugar was trying to make up for not being able to fire her the previous week.
Week 12 - Tom deserved to win... but only because Helen and Susan completely blew it. Jim was just there to make up the numbers, he was never going to be hired (and didn't deserve to be). Helen had a really poorly conceived plan, and Susan fell victim to the misconception that just because you have more experience in a certain industry than most people, it automatically makes you an expert. Tom at least came up with a workable idea and had an existing business to work with, and was the most knowledgeable of the four when it came to running a business, so he deserved to win pretty much by default.