It has been a while since we had a true villain. And those you can classify as villains usually have incredibly broad goals that aren't realistic for them to accomplish. Jihn seems to have one goals, kill someone that he deems "worthy", and he seems extremely competent at achieving that goal time and time again if we go his VO. It's pretty eerie to think that a man like that is in Runeterra right now planning to kill one of your favorite champions. He serves as a nice wildcard.