4. He Has No Weaknesses
Another major factor that makes superheroes work as realized characters instead of one note ideas is their innate weaknesses. The audience can become invested in a character that has a crippling outside hindrance or an internal affair that plagues them. Superman has no weaknesses other than a rock that's located thousands of miles from Earth and in increasingly short supply. If you're a villain and you can't get your hands on this incredibly rare mineral then you have no chance at all of your grand, evil scheme resulting in a success. Kryptonite doesn't even fully cripple Superman's powers unless it's very close to him and even then it still doesn't physically hurt him enough to be a true weakness. Compare that to Thor who is still an incredibly overpowered superhero but also one who relies on his hammer for his power. Thor's weakness is also his greatest strength, which serves to keep him intriguing. Loki is very important to Thor's development as well. Superman needs a Loki to balance him out so he isn't just this un-stoppable godlike force of nature.