Lex Luthor's Largest Error

Of source, his opinion of Kryptonians prevented him from seeing the answer.

If he had had recognition as 'the world's greatest scientist, etc., he might not have fallen as far into evil. And his source of incredibly advanced science was readily in his grasp.

Kara Zor-El, last survivor (much of the time) of Kryptonian science. Remember, thanks to Kryptonian educational techniques, Kryptonian children (well, the smart ones, and she was supposed to be very smart) learned calculus by age 4. Her parents were two great scientists, who doubtless had colleagues over for dinner, where they talked shop on occasion. She may not have learned the fine details of 'Axniff's Theory of the Twelfth Force' but she did learn the grade-school-stuff -- well beyond calculus and our science, and she reasonably had general ideas of much of the more advanced material.