Been qute a while, but my newest proposal is for one of the Halo franchise's chief villains, the Prophet of Truth.
What is Halo?[]
Halo is a long-running, critically and commercially successful sci-fi video game series centered around Master Chief and his incredible exploits for saving the galaxy during an intergalactic war against an alien race known as the Covenant, and later other entities such as the Prometheans and the Created.
Who is the Prophet of Truth and what has he done?[]
The Prophet of Truth, born Ord Casto, is one of the three high leaders of the Covenant, and arguably the ringleader of the three. As one of the head honchos of the war against humanity, the Prophet of Truth started out in minor positions within the Covenant before ascending to the rank of Prophet of Truth. At some point prior to the events of the video game series, the three high Prophets learned from the Oracle, a fragment of the AI Mendicant Bias, that the prophecy their faith was built upon, that they were not in fact the ones who would be ascended to the Forerunners and saved from galactic calamity, and that it was actually the human race who had been chosen by the Forerunners, the three of them, at Truth's behest, decided to cover it up and wage their war against humanity with the intention of wiping all of them out, all while Truth secretly plotted to become a god once humanity was slaughtered.
Throughout the events of both Halo 2 and Halo 3, Truth continuously sought more power, including betraying the Sangheli (Elite) species for the more brutish Jiralhanae (Brute) species and essentially turning their most accomplished warrior, Thel Vadamee, into the Arbiter, more or less turning him into a slave for their cause, which included killing any "dissenters" that happened to know the truth behind the High Prophet's falsehoods.
The most damning of Truth's crimes, though, was knowing fully well that the Halo rings do not kill the Flood but rather every other species that the Flood feeds on, and intending to activate all of them at once to cause galactic genocide for not just humans, but for nearly every living creature all in the name of fulfilling a prophecy that Truth already knows is a lie. In his final moments, he manages to shoot and kill Miranda Keyes before she can stop the activation, as well as attempt to forcefully use Sgt. Johnson to begin it. Fortunately, Master Chief and the Arbiter, using their shaky and unsteady alliance with the Gravemind, manage to reach Truth and stop the activation, and Arbiter finally kills Truth and avenges his fallen comrades who were slaughtered at Truth's order.
Freudian Excuse[]
I don't know much about the books, but it's implied in those that Truth, or rather Ord Casto as he was originally born as, wasn't always so ruthless and merciless and had fully believed in the Covenant's cause and actually looked out for his peers. Within the games, however, these qualities are not shown.
Heinous standard[]
As one of the High Prophets, and eventually the one true leader of the Covenant, the Prophet of Truth essentially outranks other villains due to his goals and methods. For example, 343 Guilty Spark is an AI programmed to protect the Halo rings and see they are activated, making him an unwitting participant in the galactic genocide the Halo rings would cause. Cortana, of course, as another AI, was shown to be very compassionate prior to her corruption in Halo 5 and even then, she is shown to care for Master Chief and genuinely believes she is doing what is best for everybody. The only main villain who can really compare to the Prophet of Truth's heinous standard is the Didact , who attempted to use the Composer to wipe out humanity the same way Truth tried to do with the Halo rings. However, the Didact is shown to have actually loved someone other than himself (the Librarian, back in the time of the Forerunners).
All of the things that disqualify the other main villains from being PE (343's lack of real sentience, Didact's love of the Librarian, and Cortana's genuine belief that her goals will bring about a greater good) are all things that Truth lacks. And while his co-prophets, Mercy and Regret, still have some level of concern for their subordinates despite knowing the falsehoods of the prophecy, Truth would gladly use and kill anyone and anything after they have served a purpose for him. Furthermore, the Didact's motive for killing humanity was out of misguided blame for causing a great war and mostly just converting them into Prometheans rather than truly killing them, Truth's motive lies in his own lust for power and petty jealousy over humans being the Forerunner's chosen inheritors rather than himself. This is also in comparison to the anti-heroic Arbiter, who, like many of the Sangheli, possess a code of honor and brotherhood, something Truth could not understand even if it bit him in the ass.
Verdict[]
I absolutely believe Truth qualifies as PE based on the standards set by the Halo franchise's other villains.