Alan Tudyk's K-2SO was one of the best things to come out of Rogue One, and the moment that he died in the movie was one final blaze of glory for the Imperial droid. In an interview with Collider, Tudyk reveals that his character was originally supposed to be killed by Ben Mendelsohn's Director Krennic.
He didn't really go into detail, but Tudyk simply said, "Yeah, I got shot by Krennic." Surely that scene does more for Krennic than it does for K-2. The trailers have clips of Krennic going into the fight himself, so I guess he could have been a capable fighter before they cut it out in the reshoots. If he was the one who killed the movie's only comic relief, surely the audience would have felt a lot more resentment for Krennic.
Say what you want about Krennic, but I thought he was a terrific villain for Rogue One. Aside from being cold and relentless, he himself was being bullied by the higher-ups in the Empire — something that a lot of us can relate to. His death in the hands of the very weapon he created makes his character so tragic, and that's why he's great.
See K-2 and Krennic return when the Blu-Ray for Rogue One: A Star Wars Story comes out on April 4.