We know the Despair Event Horizon is a line when someone crosses it, then they lost all hope. The crosser might still be a good person, or take a turn to evil. However, not all who crossed it will be deemed as evil.
Not these guys.
These guys love the sense of despair. When other people lose hope, they take pleasure in it. It's not necessarily that they'll push them into despair (although they may as well overlap with the pusher); however, they will cherish the feelings of despair of many people around them, especially when directed to them. They might not be Emotion Eaters, but they sure feel good when people around them despair. Since the sense of despair is something people wanted to avoid at all cost, liking despair so much and inflicting it to others would be a good indication for the audience that this character is evil.
Their favorite line will be "Fall into despair!" or any variations thereof. They will be very fond of the Despair Gambit tactic.
Very often, they'll give a Hope Spot to their victims, and then yank it away as the last seconds, mostly thinking that despair is at its finest when the last ray of hope is destroyed right in front of their eyes. If they would instill Hope Is Scary, the merrier, that'll make people turn towards despair instead! Has a very high chance to become a Complete Monster, since one is more likely to have the mindset of For the Evulz to be one (but not always, as this is also often seen in Generic Doomsday Villain).
Don't expect them to enjoy their own despair, though.Most of the time.
There are also some villains that believe that despair is necessary, and don't seek pleasure in destroying hopes and dreams, but do so because they think they have to.
To note: This isn't Despair Event Horizon (but related). That's about a line that when crossed by someone, that someone loses all hope. An event or sorts. This trope is about someone who delights in seeing people crossing that horizon, and occasionally makes his modus operandi to make everyone fall into despair, thus a good indication that he's a villain.
Contrast with Hope Bringer and Hope Springs Eternal. Also compare with Sadist, someone who delights in someone else's pain and suffering, but the Hope Crusher can occasionally overlap with how they dislike the concept of hope and likes it better when their victims are pushed into the depths of despair. Can also overlap with those who believe that Dystopia Justifies the Means. Sometimes overlaps with Troll if they use this as one of their trolling tactics.
The Big Bad of Yes! Pretty Cure 5, Despariah, usually sat on her throne with the goal of obtaining the Dream Collet to obtain immortality, then finally shroud the people in despair. In the end, she subverts this by showing absolute fear over how the Cures won't despair no matter what. Realizing that despair is not the answer, she pulls a Heel-Face Turn.
Naruto: Pain lost everything he loved in the constant wars that ravaged his home country of Amegakure. This led him to grow into a cynical nihilist who goes to great lengths to teach his enemies to feel pain. This includes crushing every bit of hope they have left.
Konan: He [Naruto] will become the bridge that leads us to peace! And I will be a support, holding the bridge up! [...] It doesn't matter if I'm scattered to the wind! I will stop y- Tobi: You called me the darkness, didn't you? Then I will make you wilt... I will take your little rainbow bridge and its seven colors and plunge it all into darkness! When my illusion ends, so will your life.
Ms. Chono from the Yu-Gi-Oh! manga lives to crush the hearts of men, and delights in expelling students on technicalities.
In a subverted way, Kyubey of Puella Magi Madoka Magica. His goal is to stop the heat death of the universe, by making young girls make a contract with him, become Puella Magi, in which they will be doomed to despair, furthering him further to the aforementioned goal. Kyubey doesn't necessarily enjoy the role, but he's unabashed in driving girls in despair, as he thinks that having emotions to think that despair is bad... is a mental defect. But on that revelation, we all know that Kyubey is the closest thing the series got for Big Bad.
The goal of the Anti-Spiral, the ultimate Big Bad in Tengen Toppa Gurren Lagann, is to eliminate Spiral Power, which is derived from hope and courage, in hopes of preventing the Spiral Nemesis from destroying the universe. As such, they deliberately fight just beyond their opponents' abilities and dispense plenty of Hope Spots before snatching victory away in the cruelest, most unfair way possible with the aim of destroying their will to fight.
Magic Knight Rayearth: The anime-only Big Bad of the second half is one of these. Not only does she want to destroy Cephiro, she wants its citizens to completely lose their hope of salvation while she's at it. This is because she is a being that was created by their extreme fear and despair after the death of their Pillar.
Ulquiorra spends every interaction with Ichigo attempting to dash any hopes he has. He does this to the point that during their final battle, he could finished Ichigo off just in his second form alone, but transformed into his third one just to emphasized how screwed Ichigo truly was. He also does this with Orihime, although her humanity starts to rub off on him.
Aizen says this line to Urahara, Isshin and Yoruichi:
"The number of plans you have devised are equal to the amount of hopes you have. So, I will simply crush them all."
My Little Pony: Friendship Is Magic (IDW): The Nightmare Forces gave everypony in Ponyville nightmares and in issue 5 used the nightmares to kidnap Rarity in her sleep and convinced her that she will be forgotten and replaced so that they can force her to become the new Nightmare Moon. Issue 6 also has the nightmare forces trying to break Luna (and give the other ponies nightmares as well, but they broke through that). And in issue 8, the Nightmare Forces try this again with Luna, but fail.
Rise Of The Guardians has main villain Pitch, whose goal is to grow more powerful by spreading despair amongst the children of the world.
Palpatine from George Lucas' Star Wars excels at this. First, he completes Anakin Skywalker's turn to the Dark Side by telling him that the Jedi Knights have turned against him, and murdered his pregnant wife. Much later, he implements the same tactic upon Luke Skywalker by showing him the rebel fleet in a Curb-Stomp Battle, and that his close friends are horribly outnumbered on the Endor moon.
Accel World: Dusk Taker's entire character arc drives around crushing the hopes and spirit of Silver Crow, and the heroes by stealing their powers, one of their new teammates, and using blackmail to put them past their Despair Event Horizon so that it looks like it's impossible for them to win.
In The Pendragon Adventure, Saint Dane doesn't just want to beat Bobby, he wants to beat Bobby right after Bobby think's he's won - which he does on several occasions.
In his first appearance in the first book of the Chronicles Of Thomas Covenant, Lord Foul announces that his ultimate intention is to annihilate hope from the Land. He then proceeds to spend the rest of the trilogy (and the two Sequel Series) going about doing exactly that.
Many Kamen Rider villains are also pretty fond of this modus operandi.
Kamen Rider Wizard has this as specifically the bad guy's job - find Gates (victim of the week) and destroy their hopes and dreams or something they love. The despair causes the victim to become a new Phantom.
In a rare heroic example, Kamen Rider Accel's catchphrase is "Despair awaits you at the end".
Villain Protagonist Francis Underwood of House of Cards seems to take some pleasure in this, even though he doesn't generally do it for its own sake but as part of his schemes. For example, in one of his asides, after he sets Peter Russo up to fall off the wagon and end his political career with a drunken radio interview, he says with some relish "it takes just ten seconds to crush a man's ambitions." Other remarks he's made similarly indicate that he takes some pleasure in being ruthless and destroying people or "discarding" people he's done using.
Also where he quietly tells the deranged homeless man trying to get into the congressional offices: "Nobody can hear you. Nobody cares about you. Nothing will come of this." That seemed pointlessly cruel even if he was a risk to security.
Nurgle, the embodiment of despair in Warhammer and Warhammer 40K, is strengthened whenever large amounts of people start feeling it (his opposite god is the embodiment of hope), so naturally his followers tend towards this. Ironic, given that Nurgle and many of his followers are Affably Evil while Tzeentch and his followers tend to be cruel manipulative Trolls.
The Fall of New York setting supplement for Fast Company, the action rules for the JAGS system, features Dr. Nothing, a Psycho Psychotherapist who specializes in crushing the dreams of those who seek to make a difference in the Wretched Hive that New York has become. In addition to his skills as Fast Company (which makes him as Badass as any player character), he likes to Break Them by Talking as well as other dirty social tricks.
Exalted: If someone serves Oblivion willingly, you can bet your yeddim that this is a major aspect of their character. The Archbishop of Chalcedony Thurible is one of the most prominent examples: he spreads a religion that states that hope is a lie.
Terumi Yuuki from BlazBlue is an unabashed Troll who goes out of his way to make everyone around him miserable, as it's what he counts as 'interesting'. A reason was he thinks that despair is the only truth there is, it, along with hatred towards him, empowers him, and he's hell bent to make it to be the sole accepted truth of the world, claiming that everything else are lies.
In The Legend of Zelda Oracle games, the true big bads need to light "the flames of sorrow, destruction and despair" in their plan to resurrect Ganon. The first two are lit by Veran and Onox respectively, and they light the last one personally by kidnapping Zelda in broad daylight, in view of the villagers.
Rakanoth, one of Diablo's minions in Diablo III, is called the Lord of Despair. He sought to drive both the High Heavens and Sanctuary into despair by capturing Auriel, the Archangel of Hope during Diablo's invasion of the High Heavens, and only after destroying him and freeing Auriel is hope restored to both.
This is the modus operandi of Super High-School Level Despair in Dangan Ronpa. The true mastermind behind Monobear, Junko Enoshima, takes the concept to its extreme by being obsessed with her own despair as much as anyone else's: she's thrilled when her plans are thwarted, because it means she can inflict the ultimate despair on herself.
Bernkastel from Umineko no Naku Koro ni is a Troll comparable to Terumi in terms of cruelty (and if Umineko were more widespread would equal or even surpass him in notoriety) that takes absolute delight in the despair she sows.
The White in Shin Megami Tensei IVare Anthropomorphic Personifications of Humanity's despair at being forever locked in the middle of the Order Versus ChaosForever War. They seek ultimate destruction and to that end they send Flynn to the Alternate Timelines of Blasted and Infernal Tokyo, so he will see neither Law nor Chaos is the answer. They despise Neutral, the most hopeful of endings. To make Flynn despair if that doesn't work, they send him against extremely lethal entities (the Ancient of Days and Sanat Kumara). The Archangel Gabriel says they became this when they "gained knowledge beyond their ken" - which in this series is never a good thing.
Eridan Ampora from Homestuck, whose title is Prince of Hope. Don't let the title fool you, the Prince class is a destroyer of/through its aspect, and so Eridan is literally a destroyer of hope. Proving the point, after the trolls were denied entrance into the new universe they had created, Eridan took away their last hope for restoring their race by destroying the matriorb.
The cubi of clan Seme in Amber Panyko Williams' Dan and Mab's Furry Adventures feed upon the emotion of despair. Since cubi can exert some amount of Thought Control, clan Seme can create the despair upon which they feed.
"Crushing Hopes and Dreams" has become a Catch Phrase of the Gundamn! podcast, as certain Gundam fans tend to develop unrealistic expectations to which they need to administer a sometimes lethal dose of reality.
My Little Pony: Friendship Is Magic: King Sombra, the villain of "The Crystal Empire". He's more of a looming threat than a directly active villain, but despair is a recurring motif with him. His former subjects suffer from depression. One of the traps in his castle is a Lotus-Eater Machine that sticks you inside your worst nightmare, to induce you to just give up. And Sombra's downfall comes when his former subjects use a big crystal to literally weaponize their hope against him.
Discord in "The Returnof Harmony" had corrupted the rest of the Mane 6 and let them become such Jerk Asses that Twilight Sparkle just gives up on trying to save Equestria.
In Avatar: The Last Airbender, Fire Lord Ozai is told that the people of the Earth Kingdom can persist for as long as they have hope. His solution? Take away their hope by burning the kingdom to the ground.