Who are some people that thought they were great but really weren't?

Throughout history, several figures have displayed a strong belief in their own greatness despite falling short of their ambitions. For example, Napoleon Bonaparte saw himself as a brilliant military strategist and emperor, yet his overreach led to catastrophic defeats. Similarly, former President Richard Nixon believed in his political acumen, yet his involvement in the Watergate scandal ultimately tarnished his legacy. These individuals exemplify the disparity between self-perception and actual impact.