Every sequel needs a hook to differentiate itself from all the previous films in its series. The hook for Transformers: The Last Knight appears to be “What if Transformers, but evil Optimus Prime?”

The poster tagline reads “Rethink your heroes.” The trailer features a purple-eyed Optimus trying to kill his former buds Bumblebee and Mark Wahlberg. “For my world to live,” he whispers in the gravelly tones of voice actor Peter Cullen, “your world must die.”

If Optimus’s betrayal of Earth is meant as a shocking twist, though, it’s not going to work. Optimus Prime may have been conceived as a noble character, but in recent years, Michael Bay has pushed him over to the dark side. Rewatching the first four Transformers films recently, it became quite clear: Whether he’s identified as a good guy or a bad guy, movie Optimus Prime is almost always a jerk.

Cartoon Optimus Prime was a different story. On the old Generation One cartoon of the 1980s, Prime struck a much more virtuous figure. In a making-of featurette for Transformers: Age of Extinction, Cullen says he based his wonderful voice performance for Prime on his brother, who was a Marine. Describing the characteristics the Autobot leader shares with his sibling, he cites “Honor, dignity, strength, trustworthiness, responsibility, gentility, and toughness.” And in the ’80s Transformers, that’s generally how he was portrayed.

Cartoon Optimus was a warm paternal figure; even grandfatherly, at times, thanks to Cullen’s bassy voice. Movie Prime came closest to this interpretation in Michael Bay’s first live-action Transformers, where the character was still idealistic enough to say things like “freedom is the right of all sentient beings.”

Bay’s Transformers are much more violent than the TV cartoon. But at least initially, Prime seemed to regret the bloodshed (er, oilshed). “You left me no choice, brother,” he whispers over the lifeless body of Megatron. And he memorializes one of the dead Autobots by praising his newfound human allies. In that first movie, Prime seems like an old soul, but a hopeful one, too.

The shift really begins with the first sequel, Revenge of the Fallen. Although the Transformers still work with our military, their alliance quickly frays. In this next scene, he claims to withhold intelligence from the U.S. government because he’s witnessed the “human capacity for war.” Takes one to know one, Optimus!

As Prime’s frustration with humanity grows, so does his taste for violence. Instead of “You left me no choice, brother,” Prime screams “Give me your face!” as he rips apart the head of the primary antagonist in Revenge of the Fallen. This time he has a choice, and he chooses face ripping.

“I rise. You fall!” is right on the line between cool action hero one-liner and murder-bragging. By Dark of the Moon two years later, Optimus is regularly accusing humans of deceit and proudly announcing stuff like, “We will kill them all!”

After hacking Shockwave to bits (“You die!”) he gets into a massive fight with Megatron and Sentinel Prime, a former Autobot leader who betrays his comrades in an effort to resurrect their home planet, Cybertron. Optimus brutally decapitates Megatron, but this is Megatron and it’s the heat of battle, so okay fine. But then he straight-up executes a prone Sentinel Prime by shooting him in the back, and then again in the head.

At this point, Optimus Prime, hero to millions of ’80s children, is blowing away defenseless enemies. Is this Transformers or a robot reboot of Dirty Harry?

Dark of the Moon wraps up with a Cullen monologue in which Prime promises that “The day will never come that we forsake this planet and its people.” One movie later, that day came. In 2014’s Age of Extinction, Optimus regrets helping humanity (“How many more of my kind must be sacrificed to atone for your mistakes?”), fantasizes about sadistic revenge (“They slaughtered Ratchet ... I’m gonna tear them apart!”), and then “recruits” the Dinobots to his cause by threatening to murder them. “We’re giving you freedom!” he says to Grimlock while punching him in the face. After he bests this robot T-Rex in a fight, Optimus holds his sword to the Dinobot’s head and says, “You defend my family or die!” Yep, that sure sounds like freedom to me!

By the time Optimus delivers his obligatory inspirational rallying cry — “Autobots: We’re going to prove who we are, and why we’re here!” — his image as an honorable warrior has pretty much been flushed down a toilet that can turn into a potty-mouthed robot. (I remain shocked this idea hasn’t appeared in an actual Transformers movie yet.)

To recap: Movie Optimus complains about protecting mankind, and threatens to stop. He kills his enemies in cold blood, and seems to enjoy it. When “bad” Optimus shows up in The Last Knight, how will anyone know the difference?

A die-hard Transformers movie fan might argue that this was Bay’s plan all along; to gradually and subversively tarnish this icon of courage and selflessness. Our world is so poisonous, they might argue, that it’s tainted this pure soul. And I might be on board with this argument if that amount of care was put into literally any other aspect of these Transformers movies. It’s not. They’re messy, confusing, and on more than one occasion they don’t make basic visual or narrative sense.

Even if we give Bay and his writers the benefit of the doubt, and we buy the notion that this was their plan all along, that raises another question: Why? For Unicron’s sake, his name is Optimus Prime. Not Cynicus Prime, not Murderus Prime — Optimus Prime. His whole purpose is to represent optimism, fairness, and hope. If you take the one character people like in these Transformers movies, turn him into a raging a-hole, and surround him with personality-free human characters, what do you have left? I guess we’re about to find out.

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