You are not supposed to make accusations in the forums. (You should erase the name.)
Use a ticket to report that. (the Contact form on the Help page.) https://support.chess.com/customer/portal/emails/new
I have never seen anything that blatant. (His opponent said "A draw or wait 20 minutes?" in a totally lost position.)
In my opinion , that would merit a banning.
Read his chat.