By writing The Miraculous Return of Jonathan Kent Cary Bates made a contribution to all those Greatest Superman Stories Ever Told volumes yet to be published that can never be overestimated and yet there's the matter of what he did to Luthor in 1983...

In 1963, Edmond Hamilton introduced readers to a more nuanced Lex Luthor by forcing the character to choose between killing Superman in front of an adoring crowd or intentionally allowing himself to fail at this scheme so that he could save a doomed planet.  Luthor choose to act selflessly and heroically for perhaps the first time in his life and was rewarded with having the planet Lexor named in his honour.  Here, Luthor was a hero - he had used Superman to bring a dying civilization water and had presumably restored much of the scientific knowledge to a civilization that had been reduced to the lowest rungs of any dark age.  Lexor was the one place in the universe where Luthor acted honorably at all times - the people of this planet may as well have been his children.

Now Lexor only appeared about a half dozen times or so during the 1960's, but it ushered in a Luthor who possessed a certain code of ethics.  Not all the time of course, but there are a number of stories throughout the 1970's and 1980's in which we learned that there were limits to how far Luthor was willing to go with his plans.  In one of Elliot S! Maggin's novels for instance, Luthor prevented Superman's soul from falling into the hands of the Devil because in spite of Luthor's hatred for the Man of Steel, he felt that even his worst enemy didn't deserve an eternity of torment.  Luthor never told Superman what he did for him nor did he expect anything in return for his good deed, it was simply a line he would not cross.

Maggin championed this new Luthor and even established that not only was there was a time in Luthor's life when the world's greatest supervillain had come close to deciding to use his genius only to help the world, but that Luthor would likely redeem himself in the future (interestingly, this is how Maggin created LexCorp about a year before John Byrne took over).  There's a great deal of richness then, from about 1963-1983 and then Cary Bates changed all that...

In Action Comics 544 Bates introduced the New Luthor (the Green Powersuited guy).  Without warning, explanation, or even follow up details, Bates decided to have Luthor spontaneously decide to turn on the planet Lexor.  I suppose the only reason Lexor was reintroduced after disappearing from the texts sometime during the late 1960s was because Bates knew what it symbolized.  Here - again no warning, no hint, nothing - Luthor dons his new powersuit, goes out at night, steals various pieces of equipment simply out of habit and when caught, begins screaming about how much he always thought of Lexorians as nothing more than insects.  Soon after, Luthor accidentally destroys the planet and becomes "More Evil Than Ever!!!" or in Bates-speak "Same guy as before without nuance or depth and cranked up to eleven!"

I get that characters are changed every so often for whatever reason, but why is it so hard for writers to exact these changes without contradicting the best of what's come before?