When it comes to describing someone who is 'most nonindulgent', there are a few synonyms that come to mind. The first one is 'strict', which implies someone who adheres to a set of rules or standards with no tolerance for deviation. Another synonym could be 'austere', which suggests someone who is severe in their manner and demeanor and does not allow themselves or others any pleasure or luxury. A third synonym could be 'disciplined', which connotes someone who has self-control and adheres to a strict regimen or schedule. Overall, these synonyms all describe someone who is uncompromising in their behavior and does not allow themselves or others to indulge in excess or frivolity.