Signs that the Opponent is Cheating


When you wait for your opponent after pre-moving but your clock is lower
Sounds like a lag issue. Your opponent cannot influence your clock.
https://support.chess.com/article/213-how-do-i-fix-my-disconnect-lag-issues
https://support.chess.com/article/4720-online-chess-performance-optimizations

If you suspect someone is cheating. Report them.
https://support.chess.com/article/209-how-do-i-report-someone
https://support.chess.com/article/648-what-do-i-need-to-know-about-fair-play-on-chess-com
https://www.chess.com/article/view/online-chess-cheating
Discussions related to cheating, cheat detection and the likes are not allowed in the public forums. If you want to discuss topics relating to cheating, you can join the Cheating Forum Club https://www.chess.com/club/cheating-forum