Mark Hunt has failed a civil suit against UFC, president Dana Whtie and former opponent Brock Lesnar, alleging they "affirmatively circumvented and obstructed fair competition for their own benefit."
Lesnar beat New Zealander Hunt at UFC 200 in Las Vegas on July 9 last year, but tested positive for a prohibited substance on two separate occasions before and after the fight.
He received a one-year retroactive ban from the U.S. Anti-Doping Agency last week and had his Nevada fighting license revoked. But Lesnar still received a record $2.5million in base pay for his victory.
And Hunt has taken action having previously claimed the premier mixed martial arts circuit is corrupt.
"I want the UFC to understand it's not OK to keep doing what they're doing," Hunt, who earned a purse of $700,000 from UFC 200, told ESPN.com.
"They're allowing guys to do this. They had a chance to take all the money from this guy, because he's a cheater, and they didn't.
"What message is that sending to the boys and girls who want to be a fighter someday? The message is, 'You just have to cheat like this and it's OK.' In society, if you commit a crime, you pay. Why is it different in MMA? It's hurt the business, so it's even worse. They need to be held accountable for this."
Christina Denning, Hunt's lead attorney, told ESPN.com her client is seeking damages "in the millions."
Lesnar, 39, tested positive for clomiphene and its metabolite, 4-hydroxyclomiphene, following an out-of-competition urine test conducted on June 28 2016, and an in-competition urine test conducted on July 9 2016, at UFC 200 in Las Vegas.
The Nevada State Athletic Commission had already changed Lesnar's victory at UFC 200 to a no-contest. The NSAC also fined the UFC and WWE athlete $250,000 last month and suspended his fighting license for a year.