A flaw is an imperfection or a defect. Demerit can mean fault or defect but in the sense blame is being used. Most often, Demerit means the loss of a privilege to a student, someone in jail, etc...The word is not common where as flaw if more common. Much more common is disadvantage. That term most often is used to describe a person's situation in that their circumstances make success more difficult. An athlete having lots of issues or problems is at a disadvantage with his/her opponent. People living in poor conditions, or abusive homes, or bad neighborhoods are at a disadvantage to succeed. It can also mean having a poor opinion of someone and that affecting their success. For instance, a boss may have a low opinion of a worker, even thought that person may be a good worker, but that person is at a disadvantage for getting a raise or promotion.