There are villains, there are supervillains, and then there is Lex Luthor.
Superman's oldest and fiercest enemy has dogged him for almost a century by now. Whether in the form of the jack of all trades mad scientist unafraid to get his hands dirty, or the diabolical businessmen the eighties made famous, Lex Luthor has taken many forms, but his egotistical vitriolic hatred towards Superman has always endured.
And yet there are many moments where Lex shows just what good he could do if he actually sucked it up and put his back into saving the day. Whether it's taking out supervillains when the rest of the heroes fail to do so, to steps in his years-spanning long-games actually having a shocking amount of upsides to them, Lex Luthor has pulled several moments of genuine heroics out of his pants - often when the reader leasts expect it.
Lex Luthor may still be an egomaniacal scumbag, but when he sets his mind to it, he can do some real good.
10. Killed Mazahs - Forever Evil
Justice League: Forever Evil was a major storyline event for the year it came out. To summarize a VERY long and complicated event, this story saw the League do battle against one of their most classic adversaries, the Crime Syndicate of Earth-3.
Now, you would think that Lex would be on the side of the Crime Syndicate, but if anyone is going to take over this ball of dirt and water spinning through the cosmos, it's going to be him.
Lex's part in the story culminates with him taking on the evil version of Shazam, Mazahs, who turns out to actually be Alexander Luthor. Now, this Luthor has already gone through Deathstorm and Bizarro Superman by this point, so you would think that Luthor would have a hard time taking down this baddie. However, the good (?) Luthor takes advantage of a loophole in the Shazam magic system to eke out a win.
Realizing that they have the same exact voice, Luthor calls out the magic word to deactivate Mazahs' powers just long enough for Lex to land the finishing blow.