Sona
As fun as it is to play Sona, she's just not good. I never see a Sona on my team and think about how good of a pick she was. I never see Sona on the enemy team and get scared because she counter picked me with Sona. In fact, I'm usually excited to face her because it's often times a pretty easy win against her. I think she should have a buff to her E. Her E is an ability that has diminishing returns when used on her allies. Why? Why does a support have a selfish ability that is only strong on herself? It shouldn't fall off on allies is what I'm saying. It wouldn't make her lane bullying oppressive or her sustain oppressive, it would simply give her more utility and more peel for her allies.
Gl HF with dealing with her adc.