Repair disk from single user mode (fsck fails)
You can try to force fsck_hfs to rebuild the catalog by running

fsck_hfs -Rc -d /dev/disk0s2


or (if you want to avoid having to answer the prompts)

fsck_hfs -y -Rc -d /dev/disk0s2


Of course this will only fix logical damages and keep failing if the disk itself is damaged.