And speaking of careers ruined by a fighter's outside actions/comments, you could look no further than Jon Koppenhaver a.k.a. War Machine.
There is a saying that you shouldn't write a check with your mouth that your ass can't cash, but if that's the case, War Machine bounced a lot of checks. After a stint on The Ultimate Fighter, WM earned a Fight of the Night award after beating fellow castmate Jared Rollins by knockout midway through the third round.
After he lost his next match to Yoshiyuki Yoshida by submission, War Machine was released from the promotion after making disparaging remarks about the recently deceased Evan Tanner, saying that he had committed suicide because his career was over and even though medical examiners were able to prove that it was not a suicide, Machine held firm with his statements. He was also released because of his refusal of a fight offered to him by UFC matchmaker Joe Silva, a rare occurrence in the promotion.
After being cut from the UFC, Koppenhaver legally changes his name to War Machine, had a brief stint as a porn actor, and was briefly signed and then released by Bellator. The reason for his release from that promotion was again due to his big mouth when he said that he hopes that someone assassinates President Obama and every President to follow him.
He would bounce around the independent circuit picking up a decent record of 7-2 with his most recent win being a TKO victory over Roger Huerta. War Machine's mouth and attitude would get him in deeper trouble as multiple bar fights in 2009 and 2010 which would lead to him serving a year in jail.
This would cause him to stick his foot in his mouth again when he said in his blog that nothing compares to the oppression men suffer in prison and that it was “worse than oppression of Jews in Nazi Germany, worse than the slavery of Blacks in early America... I'm not exaggerating either.”
After the Huerta fight, Machine resigned with Bellator and was scheduled to fight in the Season 6 Welterweight Tournament, but was sentenced to another year in jail for a 2009 assault charge.
If he had minded his Ps and Qs, he could have had successful career in the UFC, but now we'll never know how far he could have gone in the promotion.