Rescatux was the standard for grub repair in MBR and EFI systems. It has a ton of tools. Recent updates arent compatible with new machines and the system wont load anymore. If you have a GPU+CPU machine (like a AMD A6 R4) forget to use rescatux.
However if your machine is compatible, use rescatux as it's probably the best tool for repairing boot problems, disk management and thousand of thing more.
Hirens BootCD - Hirens BootCD is a powerful, all-in-one boot disk utility that will help you resolve and make reformatting your computer easily.
Finnix - Finnix is a small, self-contained, bootable Linux CD distribution for system administrators, based...
Ultimate Boot CD - The last Boot CD you'll ever need. You need the Ultimate Boot CD if you want to:
Rufus - Rufus is a piece of software that allows you to transform a portable drive, like a flash drive or other USB drives, into a bootable drive that can be used for a variety of purposes. Read more about Rufus.
SystemRescueCd - SystemRescueCd is a Linux system rescue disk available as a bootable CD-ROM or USB stick for...
Ventoy - Ventoy is an open source tool to create bootable USB drive for ISO files.