I’m pretty sure that the first superhero character I had ever heard of when I was growing up had to be Superman, purely because of the very successful films starring the late Christopher Reeve rather than the comic books. If he was the first though, then the second one would most likely have been The Incredible Hulk, though again not through comics, but rather through the television series.
In the television adaptation, Dr David Banner (played by Bill Bixby) was a medical researcher who became irradiated with gamma rays during an experiment that went wrong. From that day, whenever he got angry, David Banner would transform into his monstrous alter ego, a big green brute of a man who becomes dubbed The Incredible Hulk (played in the series by Lou Ferrigno, a former Mr. Universe bodybuilder).
The highlight of each episode would be watching the transformation from man to monster, which saw Bill Bixby start to writhe and sweat, followed by clips showing his body increasing in size and starting to rip his clothes to shreds. His skin colour would start to go that famous shade of green, and finally, once fully transformed, Lou Ferrigno would grimace at the camera and show off his impressive phsyique.
For some reason all the sequences that then followed of the Hulk smashing and crashing his way through things seemed to be in slow motion. Presumably this was to try and give more of an impressive feeling to the strength of the Hulk, and to hide how easy it would have been for Ferrigno to pick up and hurl a polystyrene boulder.