https://www.chess.com/article/view/online-chess-cheating
On average, it's around 0.2%, though the prevalence can be higher, especially at the higher rating level
https://support.chess.com/article/648-what-do-i-need-to-know-about-fair-play-on-chess-com
That said, discussions of cheating, potential cheating, or cheat detection are not allowed in the general forums. Once you account has been open for 30 days, you can join the following club to discuss:
https://www.chess.com/club/cheating-forum
I signed up for this web site a couple of weeks ago, and I'm trying to learn the game.
Not that being familiar just yet with the site navigation, I just realized I have six or seven messages in my inbox stating that my opponent violated the fair play policy, and my experience number has been adjusted.
The way I look at it, if someone wants to win that bad in a casual beginner game, just chat-message me, and I will resign.
I have to ask, how prevalent is cheating in the chess community?