Blind Without 'Em: Eridan really can't see anything more than a few feet away clearly without his glasses.
The Chew Toy: Even in an AU, the universe seems to hate Eridan.
It's All About Me: The real reason he'll never find matespritship. All of his pity is aimed at himself, he blames everything wrong in his life on other people (never himself), and the only pity he'll ever draw is for being messed up and not for being put upon by the world, like he thinks he is.
Wholesome Crossdresser: Has to borrow one of Feferi's skirts to wear on his date with Nepeta, as everything of his is dirty or in horrible condition. Also revealed to have done this a few times before in the past due to losing bets with Vriska.
This is eventually deconstructed after Eridan calls her out for trying to manipulate his and Feferi's qudrants, telling her she's no better than the bigoted and abusive highbloods. Nepeta ends up feeling so guilty that she destroys her shipping wall and gives up matchmaking.
Rage Against the Heavens: He hates the church of the Sufferer, all of its worshipers, and the Sufferer himself. When he meets/hallucinates the Sufferer in a near-death experience, he practically hate-flirts with him.
Workaholic: Sleeps about once a fortnight on average. His near-death experience after being shot with Ahab's Crosshairs wasn't because of the initial wound and catastrophic blood loss so much as refusal to stop working after being shot.
Less this and more that he's in denial to himself until his Hate Epiphany.
This trope can also be applied to his flushed feelings for Tavros, who he has flushed feeling for. However, he refuses to admit it because he feels that, as a lowblood, it would be out of place for him to pursue a matespritship with him.
Gadgeteer Genius: Builds a robot meant to resemble his childhood crush (Empress Aradia); however he's had to take so many parts from Sarada that it no longer looks much like Aradia at all.
Cannot Spit It Out: He has flushed feelings for Equius, but can't bring himself to admit it because he's afraid Equius will accept his feelings purely out of a sense of obligation instead of reciprocation.
Kick the Dog: Despite being just as much of a nice guy for the most part as in canon, his first speaking scene is after he's murdered a troll spy he was supposed to arrest and is acting more concerned about how to woo her crying lusus away.
Hearing Voices: Not only is he tormented by the voices of the imminently deceased, his divided mind regularly slips into the canon Homestuck universe. He eventually needed to be put under electroshock treatment because he wouldn't stop painting the walls with his blood and screaming that the meteors were coming soon.
Kick the Dog: Off-handedly murders a lowblood character for protesting Aradia and the hemospectrum right after we're given the character's sob story.
Hypocritical Humor: Not long after, he's kicked out of the library, which has a no poltergeist policy. While standing over the ashes of his murder victim, he gripes, "GHOSTS ARE TROLLS TOO!"
The Casanova: She seduces, fills a red pail, and throws away... only to return when the broken heart hates her, fill a black pail, and throw away for good. However, as a mild subversion, she's doing this not just for her own pleasure but as the beginning of a multi-generational project to create a new race of sun-resistant trolls.
Non-Ironic Clown: She's a member of the clown cult, but nowhere near as freaky or psychotic as Gamzee. Other than the face paint, MiRaClE Modus, clown emotes :o), and love of Faygo, there's no similarities between them at all.
Sad Clown: Played with: her face paint resembles a frowning face (as opposed to Gamzee's constantly smiling makeup), though she herself is almost always grinning. However after hearing Feferi's story her expression does temporarily turn to match the makeup.
Gossip Evolution: Some of Daivat's tabloid news casts are partially accurate. Karkat's tank getting hit by Equius turns into Karkat being assaulted by a flying blue blood. Likewise, Eridan sneaking into his respiteblock in the Royal Hive turns into the hive being attacked by terrorists with intent to kill Karkat. Word of God says that one of the articles is 100% accurate, but it's up to the readers which one it is.
Nay-Theist: He's descended from the Sufferer, but he wants absolutely nothing to do with religion.
Not So Above It All: He goes into a panic at the thought of having his blood color revealed via blood test and how Karkat might react to learning someone else has his same blood color.
Strong Family Resemblance: For a given value of "family," but take off his glasses and muss up his hair and he's a dead ringer for Karkat, to the point where he regularly freaks himself out in the mirror.
Broski: I AM THE MASTOR OF THE SPACES BETWENN MINDS / I AM THE EMPOROR OFF THE HORRHOR-FILLED WAISTLAND BETWEEN DREAMS AND DETH / THE WASTLEAND YOU ARE IN / OUT SIDE OFF YOUR SOPOR-WALLED BUBBLS OF CUTSEY INOCENT SAFE IMAGANARY FAKE DREMS,.. / THIS ISS THE TRU DREAM DOMAIN / AND I AM THE DUKE OF DREAMS / AND YOU / KARKRAP FUCKTASS / ARE NOT / EVEN / A PEASSANT / YOU / ARE / NOT / EVEN / A / PISSANT.
One True Love: Doc Scratch. Although since he doesn't exist in this universe, she can only be romantically attracted to...cue balls.
Parody Sue: Hakuba is a rainbow drinker and graceful and mysterious and aloof and also very beautiful and smells like roses and is aloof and graceful and mysterious and has good fashion sense and Doc Scratch's girlfriend and Equius's half-sister and aloof and has good fashion sense and is a rainbow drinker who is graceful and mysterious...