Ronan was definitely underserved in the movie, my sole complaint about it, he's kind of a big character in DnA's Annihilation, GOTG, etc, and his motivations are a bit fuzzy here, I'd have liked a scene of him judging some people (we do get the one Nova guy, but it's too fast), and I feel like he's too evil here when in the comics (going back to the comics I know), he's more neutral.
I'm kinda stunned that they disposed of him so easily at the end of the movie, like, he really seems to be totally gone, which I find surprising.