Yah can't spell Decepticon without Decept...

Cos Decept is a word. :P ;p You also can't spell Decepticon without "Con." Does that mean they're all Greek? :D (if anything the Autobots are more Greek in terms of socio-political structure)

 

Ελλά πάμε γά καfέ! :D

I would say Starscream but hes barely a Decepticon in the shows' storyline (mostly works by himself). So, Megatron.