These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
The comic character:
Fanon Discontinuity: Originally Elektra was just a normal girl who ended up going down a very dark path after the tragedy of losing her father. In the Man Without Fear miniseries showing how Matt Murdock became Daredevil she's portrayed as having always been a psychopath, hearing voices and intentionally going looking for trouble so she could murder her assailents. In an odd parallel to Selina Kyle's prostitute past from Batman: Year One, this is one part of an otherwise well regarded series that a lot of fans would prefer to ignore.
Critical Research Failure: "[The sai is] an offensive weapon. For killing." No, it's not. It's a defensive weapon for disarming and breaking swords. A sai is capable of some pretty horrific damage against someone, but Hollywood treats it like a knife, when it's a blunt instrument.
So Okay, It's Average: It's not perfect, certainly not a bad film. But the lack of anything interesting about the villains and Elektra's character didn't help it. In the end it's just bland.
They Wasted a Perfectly Good Plot: In the Daredevil film, Elektra was killed by Bullseye. Now, one would believe this is what he spin-off movie would have been about: Elektra would hunt Bullseye down. Combine that with her becoming an assassin solely to have the funds and resources to find, as well as demonstrating more of Bullseye's attraction to her in the first film to mess her up and other connections to the first film and you might have had a decent spin-off. Instead, it's a totally different movie, leaving her vengeance plot unresolved.