WARNING: The following contains spoilers for Platinum End Episode 12, "A Fine Line Between Offense and Defense," now streaming on Crunchyroll and Funimation.
Metropoliman once presented himself to Japanese society as an armored superhero, but that was just a ploy to lure out the other God candidates in this deadly battle royale. In reality, Metropoliman is a ruthless, calculating and exploitative villain who won't hesitate to crush anyone, friend or foe, to become the next God.
Metropoliman, unlike the pacifistic Kakehashi Mirai, is willing to do anything to get ahead, including the use of lethal force. His methods are extreme, and while that has put Kakehashi's team on the ropes more than once, Metro's methods finally turn against him, and he learns the same lesson that other villains eventually learn -- that fear and intimidation can't surpass trust and friendship.
Metropoliman has already sent his newest agent, Sokotani Hajime, to take Mukaido's family hostage, until Hanakago Saki used her red arrow to turn Sokotani to her and Kakehashi's side. Metro strikes back with his newest team of villains, including the disease-loving Kohinata Fuyuko and the heavily-armed Bakamatsu Ryuji, only for both of them to fall in battle against Mirai's team. Sokotani Hajime succumbs as well, and Metro, as a true anime villain, mocks the fallen warriors and deems them unworthy of fighting by his side. Then, his sole remaining ally, a masked boy with angel wings, loses his nerve and retreats.
To Metro's dismay, the masked boy cannot stand the bloodshed, and no finger sees a reason to risk his life for Metro's sake. He even mocks Metro before departing, leaving Metro alone against several enemies, most of all Kakehashi Mirai. This is reminiscent of the Girl A incident at the Great Tower, where Metro casually killed Girl A in an attempt to wipe out his true enemies. Metro also killed everyone involved at the Jinbo baseball stadium event, and it's clear by now that Metro views his allies as disposable weapons, not valued partners. This sets him apart from the happiness-seeking Kakehashi, and it's catching up to him. Metro can't keep this up for much longer, and for the first time, he must fight completely alone.
These trends paint Metropoliman as a classic anime villain -- a selfish and brutal character who uses sheer force and depravity rather than noble ideals or the power of friendship to fight. This puts Metro in such company as Captain Sosuke Aizen and Demon Lord Clayman, to name two examples. Clayman in particular tried and failed to defeat Rimuru Tempest with an army of unwilling minions. Clayman's minions fell one by one, and one of them, Milim, had never actually been under his control at all. Sosuke Aizen, meanwhile, never cared for the ten Espadas who fought for him and even turned on the last surviving one, Tier Halibel, out of sheer frustration. Serving an anime villain always turns out badly, and the same is true in Platinum End.
Metropoliman learns that these methods never turn out well, and that aggression and depravity can never truly surpass the bonds of friendship and faith. It may be just the shonen genre speaking, but for one reason or another, Metro's cruel method fall apart around him in this episode, and it seems unlikely that he can find and recruit more allies who will suit his needs. His minions tend to either die on their own, get betrayed or switch sides, and Metro can't keep this up. He must find a better reason to fight or suffer defeat despite his remarkable progress in the God candidate battle.
This selection exam is probably meant to determine which candidate is the kindest and most altruistic, and if so, Metro is doomed to fail. A selfish thug like him could never become the god of anything, no matter how many arrows or minions he collects.