If you're having trouble with a champ, you should try playing them for a bit.
And no I don't mean "IF THEY'RE SO OP THEN WHY DON'T YOU COLLECT YOUR FREELO?!?!"
You should try playing the champ because you will soon figure out "ah, I really have no good option if they do this" or "them doing this really screws me over" or "this is a large power spike, they shouldn't try to fight me at this moment". Then you can adapt the weaknesses and strengths you discover to your own play and use it against them. Eventually you are going to find someone that shits on you no matter how OP you think the champion is. You may even find you enjoy playing the champ and add them to your arsenal.
There's really no downside to it and it will help you grow as a player overall.