I decided to give him a shot if he can count or not after re-analyzing and seeing tie-in material like spin-offs and such.
What's The Work?
That Time I Got Reincarnated as a Slime is an light Novel about an worker who was reincarnated as a slime who formed an nation and befriended a dragon while trying to make a nation to enjoy his life enjoyable like in his old world. It also got Anime, Manga, and mobile & console games too.
Who Is He?
Edmaris Falmuth or later Macius Falmuth is former King of the Nation of Falmuth who would be responsible for invasion of Jura-Tempest Federation.
What Makes Him Heinous?
Heinous Standards?
Although there is the high heinous standards of the work most who outdo him have abilities or higher quality resources and can only be really fairly compared to Mariabell Rosso and Yuuki Kagurazaka but even them still are unfair comparisons as Mariabell Rosso has the Chaos Dragon to work with despite being position of royal power here and Yuuki still got powers & abilities despite being a guildmaster while Edmaris is just a simple human with no superhuman abilities with his forces not being special beyond normal knights.
Heinous Actions
He would invade the Jura-Tempest Federation after having some of his men provoke the Nations of Monsters to play victim where his men would slaugther 100+ people including Shion and Gobozo with intending to finish off the job in one week. And surrender conditions weren’t exactly better as it is either enslavement or vassal state or wiping them all out. Rimuru also theorized they likely had intentions to kill any human inside the city to silence witnesses here.
In ISEKAI Memories event Dark Horzions it show a alternate timeline where Rimuru fell and lead to nearly everyone killed with any survivors horribly enslaved and abused when nation of Falmuth has city occupied showing what would happen had he win prevents his invasion from being Fridge-Horror.
And all the men in panels seen in those panels of this Manga shown in the canon Trinity in Tempest spin-off make them a extension of Edmaris heinousness due to being his soldiers.
When Rimuru return back to his nation and saw horror of what happened to his nation it pushes him into his breaking point and when wave 2 came one week later with 20,000 soldiers came to finish the job it forced Rimuru to wipe out all of them due to room to negotiation the as many innocents would’ve died and to undo the deaths of the first wave.
This would make him responsible for forcing Rimuru to resort to it here and Edmaris cowardly tried to save his own spine here even trying to fake negotiate Rimuru and play dumb which Rimuru didn’t fall for.
Possible Preventing Factors
Although having his arm blown off by Rimuru and later tortured by Shion is brutal, he brought it upon himself especially when tried to lie to former to save his own spine earlier.
Despite his intentions of seeing Rimuru’s nation as a trade rival him and wanting to elminate it to free up trade and steal their technologies it make it too petty given many innocents would be butchered to do it.
What Makes Him Inconsistent?
The reason he can’t be PE or NPE is he redeems himself after being captured as prisoner and learning the hardway he forits the throne and let Youm be his successor as regret for his foolish actions. There he spends rest of the series as a Neural Character being a advisor to his successor.
He also cares for his son Edgar, his two brothers and brother Edward somewhat, he also care for his nation to extent given trade going to Rimuru's nation why he did it despite the intentions not holding up much.
He also shown to gotten along with Folgen, Reyhiem, and Razen in addition.
Verdict
Up to you all to decide.