I know a former NCO that is being overworked and it'seems affecting their personal life in many ways. The chain knows but do not care.

The chain of command has been notified. The open door policy has been used as well. There is alot of work in that particular mos and the officers expect things to get done the day They notify the NCO. They sometimes call the NCO in weekends or have them stay until late at night. There are more people that work in the section but they always task the same person.

Almost sounds like the NCO is a victim of his own success. The officers specifically task him because they know he gets the job done and quickly.
It also sounds like he needs to 'share the wealth,' so to speak. You said there are more people in the section. Well, if they are junior enlisted then the NCO needs to start passing down some of those taskings to give them experience. If they are NCOs of equal or higher rank, then he needs to put out a call for help from them. If they refuse to help he needs to take it up with command--not that he is being overworked, but because his fellow soldiers refuse to help him when it is needed.
Also, he needs to NOT be afraid to tell an officer a job will take more than one day. If they don't like it and nothing can be done, tough. That's life. Should they threaten him with a bad NCOER, then he needs to go discuss his options with IG.
A shop should not be so dependent upon a single individual when it is not a one-man shop, especially if there are plenty of other qualified soldiers to help. Otherwise, when he leaves, the shop will be screwed because their work flow will ground to a halt compared to what it was. And people notice those things.

Completely true. The NCO does ask for help and they all tend to ignore the NCO. The rest of the shop are E-5 or above and the NCO is the highest in time and grade. As of now the CO has been informed but nothing has been done and the NCO is starting to get so overwhelmed. Another thing that caught attention is how they give a negative counseling left and right if things are not done in time. I have seem them myself. The NCO gets tasked out daily with last minute things and if its not completed they get a counseling. I think is pretty ridiculous and its seems like they are trying to build paperwork against the NCO. Thank you so much for your advise I just needed a second opinion.

Based upon what you have said, it sounds like the NCO needs to exercise the open door policy with the CSM. If he is the most senior NCO and his junior NCOs aren't coming to his aid, and the officers in the shop are not backing him up, there is a serious problem. Another thing that sounds suspicious is receiving a task at the last second and then being counseled for not having things done in a timely manner. I don't know if the shop is a medical maintenance shop, a motorpool, or what, but if the NCO is expected to rush through work orders, that can lead to safety issues. If the CO has had adequate time to investigate and still not done anything, the issue needs to be brought to the attention of someone at a higher level (i.e. CSM). The NCO should be keeping a record of times when he has requested aid and received none, how the majority of the work orders are being placed upon him, and the times he has brought these issues up to his leadership and nothing has been done. Just remind the NCO, when he presents these issues to a higher up, no matter how stressed he may be, make certain he does so in a calm, professional matter. Good luck to him.

No they still are. I just found out I can't edit posts here. But the NCO is the only one in the shop there is only two other officers.