Mirko Cro Cop has had the biggest fall from grace, in my opinion.
He was destroying everybody so badly in Pride, then when he came to the UFC, he wasn't the same fighter at all. His movement wasn't even close to being the same and that was a HUGE part of his game. He got KO'd by Gonzaga and was never the same, wasn't even half the fighter he was in Pride and just fell off from there rather quickly.
Mirko simply wasn't comfortable with fighting in the cage. Some people act like that's an excuse - but seriously, Mirko had been fighting in a ring for his entire career until he got to the UFC. Mirko had been fighting professionally in a ring for 11 years by time he was signed to the UFC. He started his pro kickboxing in 1996 and when he went over to MMA, he was still in a ring up until 2007, so he was in a ring for 11 years, pretty much.
So, all of Mirko's training had been in a ring. I'm pretty sure the guy didn't even have an octagon in his gym to train in for his debut in the UFC and his first 3 fights there. He then went back into the ring after his loss to Kongo (didn't Kongo just assault his nutsack with knees the entire time? I forget) and eventually came back to the UFC not that long after since that's where the real money and competition is.
He just wasn't used to the octagon. He couldn't move around as freely as he did in the ring, where he always trained and always competed. Mirko was sensational in the ring. His movement was just crazy to watch. The way he cut angles around his opponent and countered them with that straight left and how he was able to set up his head kick, man, he was truly something to watch. Then, in the UFC, he didn't move around like he used to at all. He just couldn't, he wasn't comfortable with being in the cage, he wasn't used to the environment and I really do believe that effected him.
He was KTFO by Gonzaga and was never the same after. Mirko was never the same after that head kick loss to Gonzaga, that was a brutal loss. After that, he just declined. He just wasn't the same fighter, wasn't even half the fighter he was in Pride.
The fact he had such a long career already by time he got in the UFC is something to take into consideration, along with not being comfortable in the cage and IIRC, didn't even have a cage to train in for quite awhile, then getting KTFO by Gonzaga via head kick, if karma exists, then that's fucking karma right there.
Some may call it an excuse and that the competition in the UFC is just better, but seriously, he lost to Gonzaga via head kick KO after having an amazing career in Pride fighting the best HW's in the world. Pride had THE best HW's in the world for many years. He fought Fedor and went to fucking war with him. Fought Nogueira and went to fucking war with him. He fought TONS of HW's in Pride that would've destroyed Gonzaga so easily.
The ring was a HUGE thing with Mirko. The ring is his home. Some people are better in a ring, some people are better in a cage. Every fighter is different. If Mayweather had to fight in a cage (yes, in boxing), I'm sure he would still win but I bet he wouldn't be as effective and dominant as he is in the ring. He has spent his entire career in the ring. Training there and fighting there. Making a sudden switch to a completely different stage, from a ring to a cage that has such a different shape to it that short of a time, and also because he (Mirko) didn't have a cage to train in (I'm pretty sure he said he didn't have a cage in his gym to train it for a good while, not sure if he even has one now, honestly), that's a pretty big factor and can change a lot of things. Let's not forget about the different rules, too. Gonzaga's elbows were a big factor in his fight with Mirko, Mirko wasn't used to that and got destroyed by them on the mat and then demolished by that head kick on the feet after taking a beating on the mat.
So, if I have to pick any fighter who has had the biggest fall from grace in not just the UFC, but in all of MMA, I would say Mirko Cro Cop. He went from one of the most feared HW's in the world to not even top 10 in quite a short while, honestly. It's pretty sad, too. It's actually sad seeing Mirko lose by KO.
Anyway, this msg is long enough. See ya later by's!!!