9. The Constructicons (G1)
The Constructicons, a Decpticon group consisting of Scrapper, Bonecrusher, Scavenger, Mixmaster, Hook, and Long Haul, are engineers and builders. The Constructicons, unsurprisingly, work in construction, typically building whatever Lord Megatron requires. However, they're not just your average transforming robots, they are also, the first combining transformers. The six merge their minds and bodies to create Devastator!
With a name like Devastator, there's no way they're good guys, right? Well, interestingly, in the Generation 1 cartoon, they were not Decpticons but were peaceful guardians for Cybertron, along with Omega Surpreme. The six were busy building the Crystal City when Megatron secretly reprogramed them to destroy their creation.
They then proceeded to demolish the city and betray Autobot Omega Supreme. Since then, the combining construction crew have been servants of the Decepticons, claiming that nothing can withstand the might of Devastator!