What is considered a good bad and broken win rate

52+% winrate and a 5+% playrate means that the champion might be approaching broken status. This differs based on the skill of the champion. E.G. being 53% winrate 7% playrate is usual but being 53% winrate 7% playrate means something is really wrong.

Good winrate: 48%-52%

Bad Winrate: <48%

Overtuned Winrate: 53%-56%

Broken Winrate: 57%>

A good example of a broken Winrate would be Skarner's 63% winrate when his rework first came out

Depends on the complexity of the champ.

If a has a winrate of 53-54%, that isn't high(54 being the highest acceptable).

If or have a winrate of 51-52%, they are way overtuned.

55% winrate for people with a lot of games on a champion seems most appropriate.

a champion usually has below 50% winrate for people who pick him up for the first couple of games, since theyre still learning. mostly the meta sheep who jump from one champion to the next depending on whats played in tournaments.

youll often find that champions with a very high pick rate have a deflated average winrate due to many people jumping on the champion at the same time, and proficient mains being far outweighted by people who pick the champion up for their first couple games.

for example had a below 45% average winrate, yet received nerfs. thats because he has a steep learning curve and very few people stick with the champion to main him. those who do, are ridiculously effective with him and managed to rack up far above 55% winrate.

the tricky part is the play rate in relation to the winrate. if a champion has an extemely low play rate, even an above 50% winrate isnt much of a reliable indicator of the strength of a champion. it usually still means the champion is terrible and far too much of a nieche champion and only picked into extremely rare favourable matchups, while unfavourable matchups are massively more common and the champion isnt worth picking in most cases.

it also makes the winrate statistics as a whole incredibly unreliable due to the small sample size.