The first trailer for The Batman was only released a few days ago, but the internet is already ablaze with almost as many theories as there have been jokes about Twilight and My Chemical Romance. A particularly interesting one though speculates that the origin of the Riddler came about as a result of Batman’s decisions.
One of The Dark Knight’s core tenets of operating is that he’ll never take a life and this fan theory, put forward by Reddit user Mikhail10, suggests that at some point this policy of non-lethality affected Riddler directly.
“So what if the Riddler is trying to prove a point here [by murdering Gotham’s mayor]? I believe the following – the reason why Riddler starts killing is that due to Batman’s inaction/unwillingness to kill, the Riddler or someone close to him gets hurt. That could also partially explain why the Batman seems so much more brutal in the trailer than regular – because he wasn’t brutal enough he created a serial killer.”
It’s a solid theory, and is consistent with the dark tone the film is aiming for. It makes the stakes for Batman more personal since the deaths are due to his own choices, and is a bleak interpretation of Riddler’s primary motivation of wanting to prove himself in such a way that makes people appreciate his intellect. Forcing the World’s Greatest Detective to figure out a mystery he’s a part of that was created by the Riddler himself is entirely in keeping with the villain’s egocentric narcissism as well.
It also ties in with the Batman: Hush arc, where Riddler deduces Batman’s identity and creates the titular antagonist to dismantle the hero’s life and prove him to be unworthy of the respect he’s afforded.
In the comics, the Riddler doesn’t have a particularly sudden origin, just an obsession with puzzles from a young age that developed into combining them with crime. While becoming a slasher-like killer is not a typical interpretation of his motivations, a desire to prove how much greater his understanding is of the interconnectedness of cause and effect while outsmarting the Batman, one of the most intelligent people alive, in the process of making a point to him, is entirely plausible.