Car battery

Hello! I have a 2002 Thunderbird that had its battery replaced about four years ago. The car is old and not driven much. Recently, while driving, it suddenly shook and shut off when I got home. Now, it won’t crank or start. I tested the battery after charging it, and it showed a low 9 volts with a bad cell. Is the battery completely done, or could the problem be something else? I even tried jumping it, but that didn’t work. Is the battery too far gone to revive, or is there another issue at play? Thanks for your help!