The Riddler

The Riddler is an enigmatic supervillain who is Batman's secondary archenemy. He uses riddles, puzzles, conundrums and deathtraps. He brings out the detective work in Batman and does everything he can to defeat the Dark Knight. The Riddler has joined with three supervillain teams formed with two purposes; world domination and destroying the Justice League. These supervillain teams are the Legion of Doom, Injustice League and the Secret Society.

He was one of the three Batman enemies to find out Batman's secret identity. The other two being Joker and Hugo Strange.

Batman
After Batman ruined his plot, the Riddler had been obsessed with proving his intellect towards Batman. His obsession got so much worse that even his allies such as the Joker felt bad for him. Eventually, he found out Batman's secret identity.

Joker
The Riddler is the only villain the Joker admires. The two would always work together to take down Batman.

Kristen Kringle
Kristen Kringle was the first woman he ever fell in love with during his time in the GCPD. However, he learned that she was in an abusive relationship. He accidentally murdered her boyfriend. When he confessed to her, he accidentally killed her too. His dark side took over, thus becoming the Riddler.

Jim Gordon
When the Riddler was still working with the GCPD, he was the only one who understood Edward Nygma. However, after being exposed for the murder of Tom Dougherty and Kristen Kringle, the Riddler swore revenge on the GCPD and Gotham. However, he was stopped by Batman.