The word for a person who is excessively fastidious and demanding about details is “perfectionist.” A perfectionist sets exceptionally high standards and may focus intensely on errors, precision, and flaws that others would consider minor.
The word combines “perfection” with the suffix “-ist,” meaning a person associated with a particular belief, practice, or approach. Although striving for excellence can be useful, perfectionism usually implies that anything short of an ideal result feels unacceptable. That distinction separates a perfectionist from someone who is simply careful or conscientious.
A common mix-up is “maximalist,” which describes someone who favours the greatest, most extensive, or most ambitious option, and “minimalist,” which describes someone who prefers simplicity or very few elements. Neither word specifically means demanding flawless detail. “Imperfectionist” is not the standard answer for this definition; it would suggest someone who accepts or embraces imperfection rather than someone obsessed with eliminating it.
In psychology, perfectionism is studied as a trait with both potentially productive and potentially harmful forms. High standards can support achievement, while fear of mistakes and relentless self-criticism can contribute to stress and anxiety.