Izuku Midoriya was always intelligent, he just didn't have the ability to put his inventions together. The materials weren't in existence.
Then...
A green portal appears and an old guy comes out with a kid Izuku's age.
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Skills:
Immense IQ: Izuku is as intelligent as Rick Sanchez.
Quirk Analysis: By simply viewing a Quirk in use he can instantly figure out what it can or can't do, limitations and drawbacks as well as ways to enhance/neutralise it efficiently.
Engineering: Izuku could easily have a Degree in Engineering and can build literally anything as long as he has the materials.
Biology: Izuku could easily have a Degree in Biology and can alter the biological make up of nearly any being with ease.
Chemistry: Izuku could easily have a Degree in Chemistry, and can create substances that can travel the Multiverse.
Drunkard: Izuku can ingest toxic levels of alcohol yet still he fully capable of combat and inventing.
Combat: Izuku has ingenuity beyond regular human perception, able to use anything to do almost anything else.
Detective: Izuku can see point A and point C and get to it through Point Z.
