worst enemy, Lex Luthor had red hair when he first appeared
in Action Comics # 23. It was in Superman # 61 that Superman
found out about Kryptonite, and found that he was really
from Krypton. In 1986, to clean up story continuity from
the past 48 years, DC and John Byrne produced, a six issue
mini series, to redefine Superman for his second 50 years.
In 1992, Superman was "killed off" by Doomsday, and you
almost thought he wouldn't be back. He did return, and several
battles later, figured out a way to defeat Doomsday, at
least, so far.