How to delete the root crontab in the GRUB command line?

Question

I was experimenting something related to rtcwake in the root crontab, and the sleep worked correctly but I don't know what exactly went wrong, but now every time the PC boots up, the spinning loader animation stops in the final step of booting (the bit when all my cron commands are usually executed) and just powers off.

My guess now is the crontab commands have something killing the pc startup. In my mind I have only 2 solutions,
1.Formatting the PC (Alot of work and setting up that i won't be able to do anytime soon)
2.Clearing the crontab from the command line that I can access from the GRUB Menu (before booting).{This is what i am asking how to do??}

Answer 1

Before you do anything too drastic, try booting from a live system (e.g. the Ubuntu installer ISO written on a USB stick), mount the root filesystem from that broken installation and try to repair from there.

I don't think you can do file operations like deleting, copying or editing from the Grub shell. But from a live system you can do that with the usual tools.