Sformat is the best SCSI disk tool, I came across in the last 20 years.
It is able to repair and format nearly any disk, as long as its heads
are still in working condition and a few percent of its blocks are
writable. Once you have learned to use it, you will never think of using
something else. Formating a disk with sformat does not only send a
scsi-format command to the disk, but also make a detailed surface
analysis after formating. The defect lists are updated, and you come out
with a reliable disk, again. Thanks Joerg.

On the other side, like with any other powerful tool, you have to invest
some time in learning. Well invested time.