#3 Asafa Powell
Asafa Powell was once the fastest athlete with 9.74 seconds in 100 meters. Powell also holds the world record of breaking 10 seconds barrier for 97 times -- the highest ever by any individual. Powell was part of the Jamaican Relay team and received the gold in 2016 Rio Olympics.
But Powell tested positive for the infamous proscribed drug 'oxilofrine' in June 2013. Sherone Simpson, a fellow athlete also tested positive for the same chemical. But Powell made a clear stand that he was totally unaware of consuming any banned chemical as he was participating in camp.
But this wasn't enough to alter the ruling of International Olympic Committee. On 10 April 2014, Powell and Simpson received an 18-month suspension.