Murdering psychopath is the best description.
Killing Decepticons during combat is one thing, but when Optimus Prime approaches and already defeated enemy, and asks 'any last words, Decepticon.' Optimus has already decided on killing him.
That's not Optimus Prime; that's Judge Dredd.

 

Fair points; Megatron's brutal triumph over Sentinel was most certainly rendered void when he looked up and noted Cybertron's destruction.

But personally, I feel Megatron's call of a truce, even with Cybertron gone, wasn't genuine. I mean, he asks for it right after his air-force and end-game plan has been destroyed, so it just strikes me as a desperate last resort to prevent it being a total loss. If Optimus accepts the truce, than Megs gets what remains of his army and essential diplomatic immunity from the other Autobots/humans; not the victory he envisioned, but it's one where he gets off the hook. Megatron had three years in hiding to consider his options, if a truce was even among them at that point, but he persisted with the one that ended with dead Autobots and human slaves.

That said, I do admire his persistence, however badly it would screw humanity over  

I guess we'll just agree to disagree, my friend. We probably won't see eye-to-eye on this. But nevertheless, I had a fun debate!  

I dunno, man, I think it might be better to be a lowly data clerk than to have to experience/fight in a genocidal civil war  

 

I have to agree that Optimus and Megatron get the most development throghout the movies, essentially becoming polar opposites by the end. In the first movie we have the brave noble Optimus and the evil brute Megatron. By the second movie we have a face-ripping Prime and a softer Megatron, heck everything he had done by that point had been to serve his master? That definitely seems to be a change in character to me.

Now by the third movie things change considerably. I felt Optimus was heartless, or sparkless, for the purists. The war has taken its toll on him and he just doesn't care who dies to end it. Before we have seen a restrained Optimus, but now he goes full on psychopathic DIE DIE DIE DECEPTICONS!!!!!!111!!!!!!!!! Megatron has become a hobo wimp, and it takes the death of cybertron and the incredibly hot Rosie Huntington to make him realize this and kick Sentinel's tailpipe. I honestly feel that his truce was somewhat sincere, and was shocked and slightly terrified when Optimus coldly killed him the way he did.

Despite all of this, I feel Bumblebee got most of the focus and screentime in the series, for obvious reasons, cough cough toys, cough cough money.

 

i hope some of the autobots fly in 2014 movie

 

Look, I'll be frank: Having the best character development in the TF movies is like being the best-looker at the leper colony. Characters remain one of the largest weaknesses in the transformers films, and their development over the course of the trilogy, doubly so.

It isn't to say that there aren't good characters, or that they receive no development at all, but it's definitely something that's the exception, rather than the rule. It's also something that is often stymied by inconsistency and a reliance on tropes and stereotypes instead of deep, realistic, or novel development. A good rule of thumb I heard once for helping determine good use of characterization was "describe the character without talking about what they look like (or their costume), or their job/profession/role in the story". Now, the transformers can kind of muddy this a bit, since their appearances and alt-modes often factor into their character, but like I said, I think it's a good rule of thumb.

So who do we have to work with? Well, let's start with Sam. Sam probably gets the most screentime of anyone in the three films, and as the protagonist, is expected to pretty much carry the story and have the greatest opportunity for development. It's important that the audience understands his character well in order to invest themselves in his conflict, and hopefully, identify with him in some way. And, well, I don't really feel like the films did a very good job of this a lot of the time. Sure, Sam's character is established, but it rarely seems to develop beyond the "Sam is growing up" arc. Throughout the films, Sam acts as a sort of everyman going through the motions of a mostly normal life, played up as a loser with the potential to be a hero. Eventually, runs around with the right macguffin and saves the day. And then the next film comes along and Sam's in another stage of life where he basically does the same thing over again. Sam really doesn't CHANGE except on a superficial level. He remains that same awkward everyman in spite of these monumental experiences, most likely because if he were to truly develop as a result of them, that he would cease to be that identifiable protagonist I mentioned earlier. Also, throughout the films (though especially in the 2nd and 3rd films), Sam's heroic-ness is basically taken as given, we don't really see how or why he's able to overcome his internal conflicts in order to address the external ones, he just sort of sacks up and everyone just goes along with it (including a dead pantheon of Primes) for the sake of the story.

Bumblebee, then? Well, he's one of the most prominent transformers (especially in the first film), and he's the closest to the protagonist, and the one the audience is supposed to see in terms of accessible humanity. And I'd say the first film does the best job of getting across what Bumblebee really "IS" at his core out of any incarnation of transformers. He's all heart, a scrapper (even if he isn't always the strongest), with a bit of something to prove and more than willing to lay his neck on the line for the people and causes he cares about. I know I'm not alone in saying that you really FELT for Bumblebee at times in the first film, such as during the scene where Sector 7 captures him. But then the second and third films came, and his character (and it's development) took a massive step back. At best, Bumblebee remained almost identical, failing to develop in any meaningful way beyond his fighting skills and bodycount (I can't really think of anything we see in Bumblebee we didn't see in the first film). At worst, he becomes literally a tool to move Sam through the action around him and in doing so to keep the story moving. So, no to Bumblebee as well, then.

Optimus and Megatron have characterizations that seemed inconsistent, incoherent, or tacked-on for the sake of the story at times, and at best, I'm going to file them under "wasted potential". At least they both took the characters to relatively new (but not completely new) territory, even if it wasn't always for the best. Most of the other characters are pretty one-dimensional, and are defined pretty much only so far as their assigned task in the story.

So who, then? I'm going to go with Sentinel Prime, I think. His character was novel (we hadn't really seen a Prime outright betray humanity to the Decepticons for the sake of Cybertron before), developed over the course of the film, and stayed consistent to itself (if only because it was confined to one film). We first establish Sentinel through the other Autobots, and we learn how strong and smart and high up in the ranks he was, but the first thing we actually SEE of him when he wakes up is a dark, violent streak. In that same sequence, we see arrogance and aggressiveness, and a contempt towards the humans that serves as massive foreshadowing. The next we see of him, he seems to have calmed down, though through dramatic irony we know it's something of an act and there's more going underneath the surface. And then comes the heel turn, which even if we saw it coming a mile away cements him as a conflicted character, either a sympathetic villain or a pragmatic savior of his own kind willing to let others pay a terrible price for their benefit (depending on which side you see him from). We continue to see his arrogance, aggressiveness, and rage, his self-righteousness in trying to convince Optimus, and at the end, he becomes a pathetic, arguably contemptible character once all his power is stripped away. It's probably about as deep as the films get in terms of character development and a cohesive arc.

 

Wheelie, of course. He starts out as a Decepticon lackey, becomes a human prisoner, learns from Jetfire that he can choose his own destiny, defects to the Autobots, and seeks asylum on earth as a political refugee. In DOTM his story arc concludes as he becomes a hero when he and Brains take down the Decepticon invasion ship.

Wheelie all the way. (I'm not saying I like Wheelie, I'm saying his character has a pretty developed arc, if you think about it.)