Here's one for you, Insect instinct and intellegence is transferred by Rna and Dna, They emerge smart knowing everything they need to know. What if you have a scientist who is working on combining insect dna with human dna, The serum gets injected into the subject during a crisis like Godzilla and some other monster fighting. The guy turns into a giant with super human reflexes but he has a flaw He has to regenerate for like 12 hours and can only stay big for only a few minutes.