What makes a champion OP.

Since the beginning of League people have argued about what makes a champion broken. I want to try address that issue but I would beg anyone that responds to refrain from using champion names , even if it is only as an example. I would like to hear what metrics people think should define a champions strength relatively to the rest of the roster. I am planning to create a poll in another post when, through discussion, we come up with some good options.

For example, my perspective at the moment is that a champions objective strength can be measured through checking their high elo OTP winrates compared to the rest of the OTPs. That is because A) we need an environment of players that make as little mistakes as possible -> we can only check high elo B) if we checked everyone instead of OTP players, we would include players that have not yet mastered the champion. C) We can easily compare the winrates to make a list when it comes to that.

Thoughts? P.S. Again, please refrain from bringing up specific champions because I would like to first establish how a champ should be measured and then create a list, not create a list and then try to cherrypick why it should be like that.