2) Kawhi Leonard
Former Spurs superstar Kawhi Leonard seemed poised to join David Robinson and Tim Duncan as the greatest players in franchise history, both of whom spent their entire careers with the team. Leonard had different plans, however. During the summer of 2017, Leonard was granted permission from the Spurs to rehab his knee injury, which the two sides disagreed on.
That proved to be a big mistake and Leonard was missing in action for the first several weeks of the season with minimal contract. When he returned, he played just nine games before being shut down again and resuming limited contact with the Spurs. Following an article that painted him in a negative light and was released by ESPN, Leonard returned to the Spurs and looked as though he might return in time for the playoffs.
Instead, he never played for the Spurs again after being shut down for the rest of the season. He later demanded a trade, and they obliged but sent him to the Toronto Raptors instead of the Los Angeles Lakers.
While that was a controversial deal at the time for the Spurs, it did net them DeMar DeRozan, Jakob Poeltl, and the pick that would turn out to be Keldon Johnson. They would later spin DeRozan and Poeltl into three firsts and five seconds, including two potential future lottery picks from the Chicago Bulls and Toronto Raptors.
Still, Leonard is widely hated among Spurs fans to this day, and that is likely never going to change. To many, he quit on the team to force his way out. He ultimately did but Leonard irreparably damaged his legacy with the Spurs.