Source: comicvine.gamespot.com

2. Brainiac 5

Querl Dox of Colu is trying to redeem a legacy of evil. And he's doing it with the most brilliant mind in history.

To give you an example, most Earthlings are said to be sixth-level intellects. Most Coluans are tenth level. Brainiac 5 is a twelve.

Living in the  far future, the Legion of Super Heroes recruited Brainy to help them with their hero-ing mission. And he did, giving them all the technology they needed for their fight against crime. The Flight Ring, the Time Bubble, all the classic Legion of Super Heroes iconography was invented by Brainiac 5 while he was bored.

He invented COMPUTO, which wasn't a good invention because it was an evil murder robot. But it was a smart one. He's also matched wits with his evil ancestor before, showing that he's the more evolved and smarter of the two. He managed to be smart enough to take a legacy of evil and turn it around, and that's pretty impressive.