Ummm...to be perfectly honest with you, at least from the photos, it looks like it's beyond help...you might try taking cuttings from the healthiest seeming bits that are left....this must have taken some time to get to this point....I'm going to guess overwatering due to poor soil mix and/or a pot that's too large....if you do take cuttings use a very small pot filled with a very chunky fast draining soil mix....good luck--I hope you can save the poor thing...Maybe someone else here will have more and/or better options for you....

That looks really not-good. I would take cuttings like shelley said above, and hope for the best.

There is (some) hope! Take cuttings, using sterilized shears, of as many of the green parts left as you can. Wipe shears with rubbing alcohol between taking each cutting. When you take the cuttings, make sure the inner stem tissue is still green.

Pot them up into a very well-draining mix (like orchid bark mixed with perlite.

Water once a week until they are rooted. You may need to lightly mist them once a day, if the leaves start withering. If the bottom most leaves in the cutting yellow really fast, remove the cutting and check the rooting stem. If it is squishy, black or brown, or shriveled, you will need to re-start the cutting, cutting the stem until you see green stem tissue.

Then, water every 7-10 days, feeding 1/4 strength water soluble fertilzer every feeding.

The pot looks way too large and there was likely root rot. I would take some cuttings as suggested, and cut back all the way back to where you have a couple of leaves. remove the plant, get rid of the soil, trim back dead roots and repot in a 50/50 good potting mix and sand in a small pot. From the looks of it you could start over with a 4" pot. They like to be root bound. Water when the soil feels 95% dry. You may be surprised there may be new shoots in a month or so. Good luck!

I have saved carnosa from that state but it was pretty touch and go. take cuttings as suggested, including putting one in just plain water

and to the others I know i just committed a sin by suggesting water rooting but:

A: all my carnosa cutting have rooted quicker in water than in soil, and i think we can agree time is of the essance.
B: when my australis died i took multiple cutting, the only one that survived was water rooted

Karen, what kind of carnosa was it? plain green? or outer variegated?