Lahmu

Lahmu is a villain from Shin Megami Tensei V, as well as a demon hailing from Babylonia. He is the leader of the demons attacking Jouin High School, and the mastermind behind the invasion of Tokyo.

What Makes Him A Hate Sink?[]

He is more or less a representation of the dangers of online predators (as well as sexual predators in general), as his tactics of persuading Sahori to join his cause are indeed very similar. Considering that he is a tentacled monster and Sahori a Japanese schoolgirl, this is likely intentional to some extent.
While it is a demon, demons such as Hayatoro show that demons are capable of understanding the concept of morality, making it clear that Lahmu chooses to be evil.
At first glance, he kills humans for food. But he encouraged Sahori into killing bullies out of spite and cruelty, which she ultimately did, even if it was her own choice. And truth be told, he feasts on humans in order to make himself stronger. And him not being malicious goes out the window once he merges with Sahori, as he engages in gleeful cruelty against his two (or three, if you count Tao) greatest enemies.
He massacred the three angels that tried to stop him out of spite. While demons do have reasons for hating angels, the angels had every reason to try to stop him, as his intentions were nothing short of horrible. And Hayatoro (who is also a demon) personally strongly disagrees with what he and his followers are doing.
He was content to follow the terms of Sahori’s deal with him. But nevertheless, he pressured Sahori into making the deal.
He and a horde of demons massacred a bunch of angels. While it's hinted that he has his reasons for doing so at first given that he hated God, he ultimately has a hypocritical hatred for YHVH, as he eventually decides to have sacrifices once he believes he himself has attained godhood. And presumably, one of the reasons that he wished to recreate the world was to commit angel genocide.
He more or less spent his time stalking Sahori (even if it was to get to know her better), which is not an admirable thing to do.
While he never really forces Sahori to do what she does, it's clear that he enjoys it whenever she kills people, hence his decision to turn her into a sociopath by taking away her ability to feel sadness (which meant she could no longer feel empathy). And he should never have persuaded Sahori to murder her two tormentors in cold blood.
At first, he loves and sympathizes with Sahori. But it's ultimately a twisted, lustful obsession. To put it in perspective, Tao truly loves and sympathizes with Sahori, but wishes for her not to take his side. Unfortunately, she does decide to take his side, though she realizes her mistake in the end. And while he showers her with gifts, he doesn't show Sahori actual affection. And he expects things in return for those gifts.
While he didn't necessarily lie to Sahori (he did remove her ability to feel sadness, as she wanted) he exaggerated how great it was to be a Nahobino. Aogami himself did not, though admittedly becoming a Nahobino does have its perks. And this was mainly due to his lustful obsession with her. Humans could not gain long-lost knowledge from demons, regardless of what they could learn from them.
His minions are shown to dislike him due to his high and mighty attitude.
He claims that he will make Sahori's life wonderful. But it's not entirely true. Though he actually does help her in a way by helping her murder the two bullies tormenting her, he also intends to corrupt Sahori, and presumably make her as evil as he is. To put it in perspective, Aogami merged with the player, but gave them freedom to choose their own path. Lahmu, however, more or less allowed both Sahori and himself to lose all their sanity by merging together, as they were both insane by themselves. And Lahmu was the dominant personality, because of his manipulations.
It's understandable that he wishes to recreate the world at first, as his reason for doing so is likely because of YHVH, who sacrifices people for his own gain. And indeed, YHVH is responsible for the suffering of demons everywhere. But not only is YHVH not in charge anymore (Lucifer is), he eventually decides to have sacrifices himself once he merges with Sahori, proving that he more or less became everything about YHVH that he hated.
He has Sahori murder her best friend, by taking away her conscience (if along with her sadness). All so that he can have Sahori for himself. This more or less destroys Sahori's last thread of humanity, though Tao gives it back to her.
While he may seem friendly and charming while he’s around Sahori, it does not change the fact that he most likely wishes to watch Tokyo and the rest of the world burn, and recreate the world so it's a living hell, more or less.
Admittedly, he was nicer to Sahori than the bullies that were attacking her were. But he did not see her as her own individual, so he did not truly care about anyone but himself. And if he succeeded in his plans, Sahori would never have gotten her humanity back.
He ends up being used as evidence that demons are nothing but enemies to humanity and that they should all be wiped out.

Trivia[]

Ironically, it's ultimately Tao's love for Sahori that proved to be his undoing. Sahori eventually realizes that while Tao did truly love her, Lahmu himself did not, as it was ultimately an obsessive lust. So she allows the Nahobino to kill her in order to kill Lahmu, which works.
He is similar to Loki, the main villain of Reincarnation of the Goddess. Loki is summoned by Akemi (the protagonist) to get vengeance on the two people who wronged him, but as the story unravels, Loki turns out to be infinitely more dangerous than the summoner himself.
It's strongly implied that he was born from the darkness in Sahori's heart (hence him representing her dark desires), but it's not entirely confirmed. This would explain why he could not comprehend Tao's power, as it was more or less the power of love. Sahori may have wished to recreate the world herself though, given how unhappy her life was.
The mask Lahmu has for a face represents that he hides his true feelings for Sahori.
In his own way, he can be considered even worse than the two girls that tormented Sahori, as they were at least honest in how they felt about her. Lahmu in contrast only pretended to love her (though he actually does sympathize with her at one point, he stops considering her to be her own person once he combines with her).
Likewise, him not viewing Sahori as her own individual seals his own fate. Lahmu only has control over Sahori while she's exactly like he is. And while he took lengths to make sure that Sahori was like himself (taking away her ability to feel sadness deprived her of empathy), the moment Sahori regained her humanity, he did not have any control over her at all. And Sahori granted the Nahobino permission to kill her if it meant killing Lahmu, as she eventually realized that his relationship with her wasn't true love, which Tao more or less feared.
Lahmu is a foil to Tao. At first glance, they both love Sahori. But ultimately, it turns out that while Tao has true love for Sahori, Lahmu has false love for her: a possessive desire. And while Tao more or less tries to help Sahori keep her humanity, Lahmu wishes to destroy Sahori's humanity.
Likewise, Aogami is one of these to Lahmu. While both theoretically love their partners at first, Aogami gives the player the freedom to make their own choices. Lahmu on the other hand takes action to corrupt Sahori into becoming exactly like himself.
And ironically, he is one to Sahori herself. While they may be the same at first glance, (they both carry deep hatred in their hearts). Sahori is ultimately a tragic villain who only turned evil because of her terrible school life, whereas Lahmu is truly evil and never felt remorse for any of his actions.
He is a foil to Nuwa. While Nuwa is also a lecherous demon who kills angels, she ultimately wants she feels is best for humanity. But Lahmu only thinks about what he wants.
He is similar to Kamoshida in that they are both sexual predators, though in Lahmu’s case it is metaphorical. In his case, he also represents the dangers of online dating (initially, he and Sahori did not meet in person), though sexual predators and online dating are not mutually exclusive. Additionally, both view themselves as kings and have a fixation for a Japanese schoolgirl.
His tactics of making Sahori believe that he was a dream come true for her (and feeling entitled to her) are indeed similar to real world sexual predators.
He can be said to represent the phrase "devil on your shoulder", as while Tao is "the angel on Sahori's shoulder”, Lahmu encourages Sahori to commit horrible acts.