This is a bit different from my other tier list. Rather than trying to objectively rank overall intelligence, I'll moreso rank them specifically on their ability to outsmart other people. So their talent won't matter unless they specifically use it to outsmart others

There is some degree of ranking within tiers, but with gifted and lower, it gets harder to do that. For the most part, anyone can outsmart someone on the same tier as them, or even lower tiers outsmarting higher tiers in some cases (like Hina tricking even byakuya into thinking she killed Sakura)

Super Geniuses is for people who can accurately predict the future through their sheer intelligence? making them hard to trick.

I have Izuru as the highest in this tier since he has every talent, and is literally made to be the smartest in danganronpa. Junko did trick him for a while, but only because he had all this talent and no experience. once he learned this, he could stop Ai junko's plan. Despite this ranking, he would be argued to the the lowest in the tier

Shinsen is right below since he virtually manipulated all events. He even has further foresight than Junko, as be knew the tragedy would happen, and helped prepare Kyoko for it

Junko is the next highest since she can predict the future, even setting up an ai to continue her will. Makoto is the only one she can't predict since his luck is so weird. Kurokuma and Shirokuma are up there with her since they're each a half of her personality, and worked both sides to ensure despair happened in Towa City

Geniuses are characters that can effortlessly manipulate entire groups, or make nearly unbeatable plans

The highest here are the other triple Zero detectives besides shinsen, and Kyoko's grandfather. Kyoko already could make Junko's game much harder for her, and solve mysteries with ease, and outsmart those well above her level. But the triple class detectives constantly outdid even her, solving 5 cases in the time she solved just one.

Kyoko and Kolichi are right on par with each other. Both can outsmart other pretty smart people, and casue trouble for their masterminds. Kokochi did better, virtually stopping his mastermind, but Tsumugi wasn't even close to Junko's level. Kyoko solved cases much better than Kokichi, as she solved then before the trials, and he usually knew the answer mainly, and just pried the answers from his suspects. I still place him a tad higher on this specific tier list since she specializes in case solving, while Kokichi Specializes in outsmarting people

Nanamura is right below Kyoko. He technically did outsmart her a little, but just barely. And she's gotten better over time, and i think she's more impressive now

Nagito literally did what Kokichi did. He's right on that level. However, I do think that relies a bit more on luck

Monica is said to be on par with Junko in intelligence, but I think that's more in tech intelligence. Her planning wasn't nearly as good, and Nagito seemed smarter on that aspect than her. However, she still isn't bad

Shuichi is one of the best detectives in the series, even solving Kokichi's unsolvable murder. However, he arguably moreso just failed to see what Kokichi was doing and messed it up. I still place hin a tad higher than Tsumugi though, as Tsumugi was virtually relying on him go solve the case. Tsumugi was also very smart, using resources and flashback lights to battle Kokichi mentally, even using them to get Maki to infiltrate and attack him. While she ended up forcing him into his final ditch effort, he was still using much less resources, so I consider him smarter still

Gifted is for characters who either were lead factors in solving cases, made some of the hardest murder mysteries, or had other equivalent feats. Like Byakuya, who outsmarted his siblings and helped solve cases. Imposter, who nearly solved a murder, only failing due to Nagito's elaborate plan. Etc

Above Average is for characters who either made decent plans, but they weren't as hard to solve. or didn't work out. And/or they showed pretty high intelligence pretty consistently. Sayaka, who made a decent plan, and could predict what Makoto was thinking. Miu, who made a plan that Kokichi said the group likely wouldn't have been able to solve if it had worked. Teruteru, who managed to sneak a weapon into the party and loll despite the Imposter's planning. Etc

Average characters were as they sound. No distinctly high or low intelligence. May have had high and/or low moments, but were generally among the norm. Hina did fool the group, including Byakuya, but that was more a low showing for hi than a high showing for her. She often considered herself "dumb". Leon and Mondo both impulsively killed, but hid it decently, although could have done way better

Below Average were characters were characters with low intelligence that were easy to manipulate. Hiro had to be convinced Kyoko wasn't a ghost. He was set up to take the fall for Celeste, and needed help to defend himself. Gonta was constantly used by Kokichi to control or manipulate the group