7. William Bell
With very limited appearances, Leonard Nimoys William Bell finally showed his true colours at the end of season 4. Having continued the work after Walter had parts of his brain removed, Bell later went on to found Massive Dynamic. After working in the Alternate Universe with Walternate before going through with his final plan in our Universe you were never quite sure where his allegiances lay. Essentially, the plan that Walter and Bell had planned all along was to destroy both Universes in order to create a new one. One that they controlled without the pollution of humankind, populating it with their own ark of selected animals and creations. Once the plan was foiled very little is known about Bell until he was involved in helping the Fringe team try to stop the Observers when they first came. Upon discovering Bell was, in fact, aiding the Observers- Walter was forced to Amber everyone (including Bell) where they were stuck until being rescued by the resistance many years later. The last we saw of Bell he was still suspended in Amber (and missing a hand), surely this wont be the last we see of him. We might even see him turn out good in the end, since there have already been hints of his softer side with the photo of Nina in his safe.
The Questions: Why did he run to the Alt Universe in the first place? Was it Walters initial crossing over, or Bells subsequent experiments that caused the tear in the fabric of the Universe? What was the true purpose of Massive Dynamic? Will he redeem himself for all the bad hes done?