From the Autobots: Computron, the combined form of the Technobots, this guy is just fantastic, always stating the survival percentage of each opponent that he is fighting:
As far as the Decepticons, I would have to go with: Menasor. The Stunticons are a team, but they are all murdering psychopaths with nothing but distain for each other. They even hate their own team-leader who has to bully them into action. Their combined form, Menasor, is a bloodthirsty maniac who suffers from Multiple Personality Disorder, because every seperate Stunticon pulls him in a different direction. This guy makes Bruticus look like a well-behaved and intelligent chap.
I have a thing for Combiners, the idea that the better the team functions as a whole, the higher the performance of their combined form is, just appeals to me. It just brings out so many interesting possibilities. Even though it's mostly the Decepticon combined forms that are shown with personality and functionality problems, the Autobot versions are equally disadvantaged.
Computron takes forever with decision making because all of his individual parts want to have a say.
Defensor can be a force of destruction, when he focusses so much on saving one individual that he wrecks everything around the objective just to complete his mission.
Superion has two simple goals that dominate his every action: one, to destroy the Decepticons and two, to protect others. His thoughts are a combination of all five Aerialbots distilled to their respective cores, with anything not relating to his primary function being suppressed. Because of his single-minded attitude, the other Autobots find Superion to be distant and unfeeling.