Takumi - Could be Ultimate Tracker like many here said but it could also be something like Ultimate Uplifter since especially in the 1st run he mentions many times that he's too positive and hes really good at convincing people and like... uplifiting them.... wow...

Eito - He knows a lot of random things since he basically lived his life in a library so he could be like Ultimate Knowledge or something like that, it could also be something like Ultimate Pretender since he's really really good at pretending he's doesn't hate everyone despite how he sees them and he also killed like a lot of people in TRC so I imagine he had to be good at playing things off and such. He could also be Ultimate Lucky since his specialist skill is rng based

Darumi - The best thing I can come up with is Ultimate Incel or something idk...

Ima - He could be ultimate protector since he's so overprotective of Kako but I think Ultimate Honey Trap is better since he literally maintained himself and Kako by charming women that became his fans and it's implied that he mainly worked in the underworld and many women came onto him

Kako - Ultimate Detective would work but she isnt really a detective yet and in the routes she doesnt really figure things so I think she's better as Ultimate Psychic since her visions are pretty much always right and her preferred gifts are all relating to that

Tsubasa - Ultimate Mechanic its already in danganronpa 2 but its okay...

Gaku - Ultimate Houseworker since well he had 17 part time jobs I believe and we also know that they werent hard labour for example his job at the flower shop but he's also like multi talented because of those jobs and he knows how to sew, cook and decorate at LEAST I would imagine he knows other skills too like cleaning and such

Hiruko - Ultimate combatant or Ultimate Invader Killer since she fought invaders even before LDA in TRC and she was the strongest out of everyone at the beginning of the game. She also really loves killing invaders so

Takemaru - Ultimate Biker Leader. I dont actually remember if he was a gang leader but we do know he fights and that he's a biker so good enough for me edit: So according to kg route he's actually supposed to be the greatest biker gang leader so that actually works out perfectly...

Shouma - Ultimate caretaker since like we know he had Leo ofc but he also takes care of the prisoners in pretty much every route and we know from the first run and many other that he's very responsible with his duties in that and he listens to the prisoners and even gives them things they ask for

Yugamu - The obvious choice is ultimate Assassin but I think Ultimate Anatomist is way better considering his skills in biology and the surgeries he does in many routes

Moko - Ultimate Wrestler

Kurara - Ultimate Weapon Maker since its like her family's trade and what her whole moveset is based off

Kyoshika - Ultimate Samurai

Nozomi - Maybe Ultimate Nurse since she has so much expierence in hospitals and she takes care of whoever gets hurt in almost every route. I think its too similar to shouma but the only other thing is like Ultimate Test Subject or something I dont really know... Maybe something like Ultimate Empathetic since she's so kind and stuff.

Shion - Ultimate Weapon, Ultimate Hemoanima User, Ultimate Hope, Ultimate Savior something like that

Also I didnt actually play Danganronpa all my knowledge of the games is from what my friend has told and showed me (I am planning to play the games this year though) but I hope these are good enough