The Decepticons are the antagonists of the series. They are typically concerned with such things as conquering Cybertron, defeating the Autobots, amassing large quantities of energon, obtain the powers of the AllSpark, developing powerful weaponry, and beating people up. Not necessarily in that order.
Unlike the Autobots, whose leader is a Prime bearing a Matrix, the Decepticons are led by the most powerful of their ranks. This tends to cause some conflict, given how generally every Decepticon thinks that they're the most powerful. Also, the Decepticons are not exactly the most compassionate beings in the universe, but not all fight for greed. More than a few have a sense of honor, while others believe that Cybertron would be better protected by aggressive expansion.
List of known DecepticonsEdit