Riven is the only champion that makes me want to ragequit when fed

Why? Her high scaling combined with mobility, and utility makes it next to impossible to go up against, even with multiple teammates. If she gets one kill on you, which isn't hard since she is a lane bully, she snowballs to the point that if you have less then 75% of your hp, she will dive you and usually succeed(Assuming you aren't a very tanky champ with cc). One kill makes the next easier, to the point where you can't go back to lane, because you will get dived. Melee ADCs ( ) can also be frustrating, but Tryndamere is the only one with a reliable escape, and Yas is the only one with hard CC. Riven has 2 hard cc's and mobility, plus her shield, making her when fed, unstoppable if played right.

I think finding a way to remove her snowbally power without nerfing her would be the best solution, but this is just my opinion of course.

EDIT: I don't think shes broken (I do believe she is a little bit too strong, but not gamebreaking), I mean she is so annoying to play against, it gets to the point you would rather not play league then deal with her. Hope that clears some stuff up.