Kyrie Irving
We can go ahead and get one of the most obvious inclusions on this list out of the way early. Kyrie Irving joined the Celtics as one of the best and most talented guards in the NBA, but by the time he left, he was looked at as a total disgrace and will likely be booed every time he returns to TD Garden for the rest of his career.
Getting Irving in Boston came as a total surprise. In July 2017, it was reported that he wanted to leave LeBron James and Cleveland in order to find a bigger role somewhere else. A little over one month later, he was officially traded to the Celtics, where he joined an instant championship contender.
After a successful first season with the team, Irving got up in front of an arena full of Celtics fans during the 2018 preseason and declared that he planned to re-sign with the organization the following summer. As everyone in Boston is aware, that is not what ended up happening.
After a disappointing campaign compared to their preseason expectations as well as a flameout in the 2019 playoffs, Kyrie ended up signing with the Brooklyn Nets in free agency, joining Kevin Durant and leaving behind the Celtics fanbase that he once publicly declared he would not leave high and dry.
Since the day he went to Brooklyn, it has been hard for fans in Boston to let go of their resentment for Irving. The superstar guard has only added fuel to the fire on his end as well, with incidents like the May 2021 playoff series between the Nets and Celtics, where Kyrie visibly and intentionally scraped his foot on 'Lucky,' the logo of the Celtics' mascot that sits midcourt at TD Garden.