I find Karin annoying actually.
-When it comes to Karin and Sakura. I prefer Sakura easy. I feel as if Karin is the most lost character, who would physically and mentally destroy herself for another who truly doesn't care for her.
I'm not saying she doesn't have a major rule in the story but she is the physical form of a fanboy/girl placed into the Naruto world. And I find that annoying personally