Hassio Won't Start after groups.yaml change

Help! Simply added a entity to my groups.yaml file and now I can no longer access my hassio web interface. SSH will not respond either to my login requests. Is there a “safe mode” or backdoor into this thing? I’ve tried rebooting, powering down etc.?

Take the sd-card out and put it into a pc, you can read and edit the config files, correcting/removing whatever you did to cause such calamity.