People keep mentioning Ryze.
All it does is show that people really have poor understanding of what 'simple' and 'complicated' means. Or rather, why the one is a good thing and the other not so much.
Ryze is actually one of the champions new players do exceptionally poorly with. His combo based spell casting is easy to mess up, leading to a drastically lower damage output. His build is completely unlike other AP carries, meaning they often build him wrong. Even now, more advanced players still rush Frozen Heart on him, despite the fact that the CDR is completely wasted on him.