Remember Starkiller from Star Wars: The Force Unleashed? Those who do will remember him as the dual saber wielding Jedi who was Darth Vader's secret apprentice. While largely ignored in the mainstream Star Wars universe, Starkiller has remained a popular character just off of the two games he's appeared in, and was almost featured in a storyline for the series Star Wars Rebels!
This is all according to voice actor for Starkiller Sam Witwer who says his character was going to serve as one of Vader's inquisitors to hunt down Jedi, but was ultimately nixed due to the overpowered nature of his character. That sucks to hear, but considering Starkiller strikes down numerous Jedi masters in the games and even goes toe to toe with Vader, I can see how the writing staff wouldn't want the headache of either making him an unstoppable villain or underpowering him and pissing off the fan base.
Let's hope someday Starkiller gets the love he deserves.