There is a report function for this. You also have no actual proof that it is an alt anyway.
Need admin 4pc help!
https://www.chess.com/variants/4-player-chess/game/33030373/31/1 he is most def not a alt...
Directly from the forum rules:
5. Do not use this forum as a means to accuse or report another player of rule-breaking.
- Rule-breakers within 4PC can be reported directly to admins. More information on how to do so can be found here.
- Rule-breakers within this forum can be reported by directly messaging an admin.
[Edit: screenshots removed]
Admin 4pc pls doing something with this alt account!