9. Invented A Kryptonite Warsuit
Lex Luthor's warsuit is one of his iconic looks. The hulking green and purple suit of power armour allows him to go one-on-one with Superman in battle and proves that, while Lex has many business interests, fashion definitely isn't one of them.
The suit first appeared in what was not even one of the weirdest Silver Age plotlines. When Lex challenges Superman to a fair fight they both travel to the planet of Lexor which orbits a red sun and so nullifies Superman's powers. However, Lex became the planet's hero after helping rebuild their society and eventually decided to give up crime and live there.
Apparently though, being constantly adored and praised can get boring after a while so Lex decided to come out of retirement and lured Superman to Lexor to try and kill him again, hoping that maybe the 900th time would be the charm.
When Superman arrived, he found Lex decked out in a suit of Lexorian armour. Not only did the suit increase his strength and durability, but it also allowed Lex to fire blasts of kryptonite energy to weaken Superman. The two fought but the battle ended when one of Lex's blasts destroyed a machine keeping the planet's core stable. Lexor was destroyed but Lex got to keep the suit, so swings and roundabouts really.
In more recent comics the suit's origin has changed to the more reasonable 'Lex hired a bunch of scientists to make it'. Still, no matter the origin, Lex's warsuit means that he is more than just an intellectual threat to the Man of Steel.