MOST NOTABLE ACHIEVEMENT can be defined as the most remarkable accomplishment or success that a person has achieved. The term is often used to describe a major milestone or event that stands out from all other accomplishments. In the crossword, the solution for MOST NOTABLE ACHIEVEMENT is CAPSTONE. A CAPSTONE is typically the final project or task that a student completes in order to graduate from a program or course of study. It is usually a large-scale project that requires the student to demonstrate their knowledge and skills in the field.