Upon his inception in 1938, Superman was far weaker than we know him to be now. He couldn't fly, instead he was able to make giant leaps of up to ? of a mile! He was only fast enough to pass an express train, and would likely have been killed if hit by that train. He also was only durable enough to withstand bullets - anything more powerful would probably have killed him.
Superman gradually accumulated more powers as the years went on, until he became the nigh-invincible character we know today. He can fly through space, travel faster than light, withstand nuclear explosions and move entire planets. It honestly seems more than a little unfair.
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