Word for a really evil troublemaker

Question

I'm looking for a word in English for someone who deliberately sets out to disrupt relationships with genuinely evil intent. Something like a cross between the Childcatcher in Chitty-Chitty-Bang-Bang and a ghoulish kind of pervert who loves to threaten people with relational chaos, like the scammers who send the "I've inserted spyware on your computer and filmed you pleasuring yourself while consuming porn, now pay me or your family and friends see the video" email, only several orders of magnitude worse. "Troublemaker" just seems too benign for this sort of person. Even "malicious" and "sadistic" don't seem sufficient for the kind of person I'm thinking of. I'm thinking, really twisted, the kind of person who would threaten parents with the idea he might both abuse their children and gaslight them into thinking the parents were the abusive ones. And if the words are gendered, I'd like them to be referencing the masculine.

Something like this:

"Misandros was not just vile and malignant; he revelled in the anguish he caused to his victims, not through physical abuse, but through playing on their thoughts and emotions as the sound of fingernails dragging down a blackboard plays on the ears of a sensitive person. He seemed to hate anyone who had good relationships and wanted to destroy both the relationships and the people involved. In short, he was a [word I'm seeking]."

Any good candidate words you can think of? Thanks.

Answer 1

The obvious answer is psychopath, defined by MW as:

a mentally unstable person; especially: a person having an egocentric and antisocial personality marked by a lack of remorse for one's actions, an absence of empathy for others, and often criminal tendencies

You could also call such a person Machiavellian, defined by Cambridge as:

using smart but often dishonest methods that deceive people so that you can win power or control

Answer 2

Since you seem to focus on the person's desire to be cruel and not the outcome, necessarily, I think 'sadist' is appropriate:

a person who enjoys being cruel

This does neither imply the plotting and scheming that other answers suggest.
It will likely need an intensifier for your purposes.

Aa an adjective, 'malignant', which you already used, would do the trick on its own:

disposed to cause harm, suffering, or distress deliberately; feeling or showing ill will or hatred.

Combined, they might overlap in meaning, but that meaning will be clear: he was a malignant sadist.

Answer 3

Tormentor:

someone who causes a person or an animal great mental suffering and unhappiness, or great physical pain (Cambridge)

The verb torment seems to describe what your character is doing:

To torment is to afflict or harass as by incessant repetition of vexations or annoyances (Collins)

Answer 4

The answer might be demonic (acting as a demon) or diabolic (behaving like the devil).

But, if such person has a constant need for admiration, attention and praise, he may be a Narcissistic pervert :

Narcissistic perversion is characterised by arrogance, selfish behaviour and a lack of consideration and empathy with others. Narcissists can draw you in and be very charming in the early stages of a relationship. However, other people can often see them for what they are: manipulative, exploitative, selfish, demanding and patronising. This pattern of behaviour affects every aspect of a narcissist's existence, from love and family relationships to work and their friendship circle.

If the monster is using trick or deception, he is mephistophelian :

If someone calls you mephistophelian, they're commenting on your devilish nature or your gleeful wickedness. For example, the supervillain known as The Joker has a particularly mephistophelian laugh.

The adjective mephistophelian is a great way to describe an evil genius or a clever, wicked person. The word comes from a demonic character in German folklore, Mephistopheles, whose name stems from mephitz, "destroyer" in Hebrew, and tophel, "liar." Your little brother might look mephistophelian in his Halloween devil costume, and you could even describe a perfectly nice man with a pointy beard as mephistophelian.

Answer 5

How about misanthrope?

Merriam-Webster:

: a person who hates or distrusts humankind

Answer 6

'Blackguard' might do what you need:

A man who behaves in a dishonourable or contemptible way.

Answer 7

Your question was,

"what is a word for a really evil troublemaker?"

One potential answer is:

"daemon" or "demon"

Answer 8

If this abuse occurs online

If the person is making bad-faith arguments and attacks to disrupt discourse and cause psychological distress in online forums, they are a troll:

a person who posts or makes inflammatory, insincere, digressive, extraneous, or off-topic messages online...with the intent of provoking others into displaying emotional responses, or manipulating others' perception, thus acting as a bully or a provocateur. The behavior is typically for the troll's amusement, or to achieve a specific result such as disrupting a rival's online activities or purposefully causing confusion or harm to other people.

If the person is deliberately interacting with others in a shared experience, such as in MMORPG, they are a griefer:

a player in a multiplayer video game who deliberately and intentionally irritates and harasses other players within the game (trolling), by using aspects of the game in unintended ways in order to destroy something another player made or built, or stealing something, such as items or loot, when that is not the primary objective. A griefer derives pleasure primarily, or exclusively, from the act of annoying other users, and as such, is a particular nuisance in online gaming communities.

Answer 9

I'm not sure there IS a single word that encapsulates everything in the excellent descriptive passage you quoted! Unless you go for deflationary humour:

"Misandros was not just vile and malignant; he revelled in the anguish he caused to his victims, not through physical abuse, but through playing on their thoughts and emotions as the sound of fingernails dragging down a blackboard plays on the ears of a sensitive person. He seemed to hate anyone who had good relationships and wanted to destroy both the relationships and the people involved. In short, he was a jerk!"