When describing a shape or a triangle, "most rightangled" can also be referred to as "most orthogonal" or "most perpendicular". The term "orthogonal" is commonly used in geometry to describe lines or vectors that are perpendicular or at right angles to each other. A more specific term is "rectangular", which describes a rectangle with four right angles. Another synonym to use would be "quadrilateral", which is a shape with four sides and four angles, including right angles in the case of a rectangular shape. With these synonyms, you can describe shapes and angles with precision and accuracy without the repetitive use of the phrase "most rightangled".