Where there is good there is also evil. To the Autobots that evil comes in the form of the Decepticons.
5: Devastator/ Menasor/ Bruticus (G1): One of the things that I really loved about watching through the first two series of G1 Transformers was seeing the formations of the combiners since they all looked awesome and before I watched this I was a huge Power Rangers fan, so it was basically seeing evil versions of the Megazords. The first combiner that we see in the series is Devastator, and he gets the upper hand for the Decepticons, but we then see them start to be defeated by the Autobot more and more frequently. However, Devastator is also good as separate vehicles since that they are based off construction vehicles so they have been useful in building structures for the Decepticons. Menasor on the other hand was designed on more of a different matter and that being to match the Autobots on the ground since that the main design motif for the Decepticons was more militarized, these seemed to be more blended in for disguise, but when they were put into battle with the Autobots they had the upper hand, until the Autobots created their counterpart and they could beat Menasor. But the most intriguing of the combiners is Bruticus for the fact the robots created for him were built from Starscream after he was kicked out of the Decepticons and was going to use them to show Megatron how resourceful he is. But the interesting thing about this was that Megatron praised Starscream for what he had done, and then he wiped the memory of the Cons used for Bruticus and used it for himself.
4: Steeljaw (Robots in Disguise): For a series that I have just gotten into I found that Steeljaw is a rather interesting Decepticon. In the show, Steeljaw is shown as a Con that only wants one thing in life and that is being ruling over a planet full of Decepticons and he would do anything and use anyone to get what he wants. In the first series of the show, he starts getting his army ready, which is made up of the typical villain of the week and uses their abilities and sometimes sacrificing them to get captured to get the job done. I think another reason why I like this character is also because of his voice actor, that being Troy Baker, who makes this role his own and gives a menacing and devious character.
3: Starscream (Various): What can I say about Starscream that people already haven’t said before. He has delusions of grandeur wanting to become the leader of the Decepticons and become respected. But on the other hand, he is also a bit of a coward. He has also had a lot of good moments to throughout the various series and incarnations of the show with some of the best coming from G1 and Cybertron. One of my favorite moments from G1 was during the Transformers Movie when Starscream decides to take advantage of an injured Megatron by casting him and some of the other Decepticons out of Astrotrain since that Astrotrain was being weighed down. With this Starscream then became the leader of the Decepticons for a hot minute before he got killed by Galvatron. Another of my favorite moments is during Cybertron when Starscream uses the Earth Cyber Key and makes himself to be a rather strong opponent to the Autobots.
2: Megatron (Various): Megatron has been the leader for the Decepticons for a long time and he has had a lot of cool transformations from a gun, to a tank, to something that resembles the Batmobile. He is a no nonsense leader and can be rather ruthless at times, but he does see the good in the ideas, sometimes, that his team has. The one that I mentioned already was seeing the brilliant idea that Starscream had when he built his own combiner and then wiping the memory of said combiner to forget that he was created by Starscream. He also has had a lot of rather good and smart ideas compared to what the Autobots have done since that during the first few episodes of G1 when they attacked places to go and gather Energon to get on their way back home to Cybertron, they use green energy sources to generate Energon and that they were successful in getting Energon out of it. But with the good there are also a lot of problems that Megatron has and he does seem that he can be rather self-destructive, blaming his team for the failures that have happened over the many years and battles with the Autobots.
1: Soundwave (G1/Prime/Robots in Disguise): I love Soundwave for so many different reasons. The first is that his transformation is useful for a lot of the plots, since that in G1 the transform modes could change their size, and a lot of the times it featured Soundwave being the size of an 80’s radio being picked up by a dumb human. The second thing that I like about him is that he has Cassette-Bots that have proved to be rather useful for the Decepticons with Laserbeak being used for surveillance and Prowl used to hunt down any humans that can get away from them. Another reason why I like Soundwave is that in later incarnations he is a powerful fighter and is also cunning. During an episode of Robots in Disguise he was able to manipulate the ground-bridge in the Autobot base to escape a pocket dimension that he was in and managed to get Bumblebee into it. He also managed to beat Strongarm and Grimlock and he was also nearly able to set his plan in motion to signal other Decepticons back to Earth but he was stopped by Bumblebee who used his own tricks against him to put him back in the pocket dimension.