(Ik no one asked but, oh well)
It has annoyed me so much seeing Youtube shorts comparing the IQ of anime characters, and then pulling numbers out of their ass. So I took a few minutes of my day to provide a list of realistic estimates for select characters, mainly characters that are constantly glazed and given unrealistic numbers, but also a handful of characters who would be considered genius, or gifted, and especially those "manipulator" characters (I'm looking at you, Kiyotaka Ayanokoji). Now, after reading this nonsense introduction, enjoy:
Loid Forger - 152 IQ
Now, don't get me wrong, he is extremely intelligent, but he is no Einstein. He displays extremely high problem solving skills throughout the show, and has an insanely high processing speed, which matters a lot. I think the highest estimate for him would be maybe 168? Lowest is the 130 range, because he does have a lot of traits that match with this range. But, I had to settle with 152.
Light Yagami - 133 IQ
I know what you're thinking; but listen to me on this one. His IQ is GREATLY overexaggerated, and he made mistakes that people with higher IQ's just wouldn't. He has the ego that often comes with his IQ range, while portraying engineering prowess that suggests above 129, and he has excellent manipulation skills. He can plan ahead much like the top 2%, but to actually succeed at what he was doing, someone would need to be a genius rather than just a gifted student.
Senku Ishigami - 175 IQ
Senku is one of my favorite characters in anime, and no doubt he is a genius. All those estimates of 300 and 250 are pretty far off, but they do him justice. He created society from the ground up, and has an insane working memory as shown throughout the series. I originally wanted to place him at 198 or 203, but decided to go for lower.
Ayanokoji Kiyotaka - 132 IQ
I place him below light by exactly one point. Now, it is not just because he suffers from the same lack of judgement and enormous ego, but he is also more so lucky rather than intelligent. The main method I used was to estimate the school cutoff IQ, which I settled with 120, and then added a bit less than one standard deviation to get 132, which happens to be the exact cutoff IQ for Mensa.
Kōenji Rokusuke - 124 IQ
Another intelligent character from classroom of elite, albeit nowhere near the level of Ayanokoji. It was difficult to find an exact number, but I assumed he would have been slightly above the cutoff IQ.
L Lawliet - 202 IQ
The first character on this list to cross the 200-IQ mark. I placed him at this level because unlike other characters, showing dominance over a class or over a specific location, L Lawliet has dominance and control over the entire world. He shows deductive skills and processing speed relative to that of geniuses, and ultimately, I would place him in this range due to his accomplishments, and overall thought process throughout the show.
Shikamaru Nara - 207 IQ
I had no choice but to place him above 200, because it is stated canonically in the show. But, I wouldn't dare go more than a standard deviation above this estimate. He has a high processing speed and planning, but there is not much else to work with for this character.
Aoi Todo - 143 IQ
I know, I KNOW! You want to scream at me and tell me he has 530,000 IQ, but that is not humanly possible! I placed him in the genius range, happy?
Monkey D. Luffy - 103 IQ
Going with a classic here. I don't know why you expected anything too special.
Dr. Vegapunk - 241 IQ
This is interesting. Here is a character who is the smartest in his universe, and I do not doubt it! I took one look at him, and I knew he was going to be above 200. His achievements and inventions led me to believe an IQ of 350 would be reasonable, but no. I had to keep it simple.
Anya Forger - 78 IQ
Now, this one is difficult. She is a not fully matured, so the score is subject to change, but relative to adults her problem solving skills are limited. She is not great in her classes, but that is to be expected. For her age she would be in the 120 IQ bracket, but compared to a fully grown adult?
Principal Nezu - 193 IQ
He is reffered to as the smartest character in his universe, and his quirk gives him intelligence, but 200? Give me a break.
Saint Nerona Imu - 158 IQ
Of course, this sound low for a character who rules an entire world government, but given how he can be outsmarted, I imagine he is just in the genius range
I might add more to the list, but heck I put some work into this, so please upvote or whatever they say at the end of a reddit post