Adrian Mutu
Adrian Mutu was doing quite well with Chelsea back in 2003 until drug tests revealed he was positive for cocaine. This failure resulted in a seven-month ban and the end of his contract with Chelsea. He also had to pay a huge €17m fine. More recently, the footballer failed another drug test and got a nine-month ban, and earlier this season he punched an opponent and was sentenced to a three-game ban. It seems like some people never learn from their mistakes.