Summit, peak, pinnacle, climax, apex, acme, culmination, meridian, zenith, apogee can mean the highest point attained or attainable.
Summit is applied to what represents the topmost level attainable by effort or to what is the highest in its type or kind of attainable things.
Peak usually implies a point rather than a level. It is frequently applied to something that is or can be represented in a graph; used absolutely it designates the highest point reached in a course or during a stated or implied length of time.
Pinnacle is applied chiefly to what has reached a dizzy and, often, insecure height.
Climax implies a scale of ascending values; it is applied to the highest point in force, in intensity, in interest, or in impressiveness in an ascending movement or series. The word often suggests an end or close.
Apex is applied to the highest or culminating point (as in time or of accomplishment) to which everything in a career, a system of thought, or a cultural development ascends and in which everything is concentrated.
Acme is applied to what embodies or represents the perfection or pure essence of a thing.
Culmination can denote an apex that is the outcome of a movement, a growth, a development, or a progress and that represents its natural end or attained objective, but often culmination suggests a coming to a head or issue rather than to a high point.
Meridian is applied to the prime or period of fullest development or vigor in a life (as of a person, a race, or an institution); it connotes not only prior ascent but ensuing decline.
Zenith adds to meridian the implications of luster and distinction.
Apogee, like meridian , is applied to the highest point (as in a course, a career, or a movement), but it seldom connotes being at the prime or height of glory.