How do I remove keychain access on a device I gave to someone that I no longer have access to?

I recently sold my laptop to a family member. The wipe didn’t occur properly and required them to put in my Apple ID to sort something out before they could put in theirs. It appears they allowed keychain access but didn’t unlink it before logging out of my ID. All my keychain passwords have now synced across all their apple devices, any time they remove them they reappear (thankfully not synced to my account or I’d have lost all my passwords). So they are getting frustrated as my username and passwords keep popping up instead of theirs. There used to be an old thread rectifying this issues but it was for IOS 12 or earlier and doesn’t work for up to date systems.

Can anyone help me rectify this issue?