https://support.chess.com/article/648-what-do-i-need-to-know-about-fair-play-on-chess-com
It's very possible a good player stated with a low rating from the initial account. The way the Glicko rating system works, is that players will have larger rating changes after games and as they play more, that value drops. So a strong players, starting with a low rating will see large increases.
However, if you feel your opponent wasn't playing fairly, you should report them.
https://support.chess.com/article/209-how-do-i-report-someone
However, discussions of cheating, potential cheating, or cheat detection are not allowed in the general forums. If you would like to discuss, join https://www.chess.com/club/cheating-forum
First game they win with 90.5 accuracy. I’ve played that before, so except his rematch.
Second game they win with a 99.6 percent accuracy. I didn't have time to check the report, and they àsk for another rematch.
Third game, another win at 99.6 percent accuracy. They ask for another rematch, but I’ve had enough.
Their rating has now jumped to 1614 in less then a day. Either they are creating, or they are a lot better then the rating said they are, and created a brand new account. I mean two 99.6 games in a row. Okay, yeah right.