In case you haven't heard of Mixed Martial Arts, it's quite an awesome sport. It's about as close as human beings could get to legalizing fights to the death in civil society. Two expertly trained athletes hurling muscle and bone at each other's body, head and legs until one goes down or somebody taps out to a submission hold. While there have been very few deaths which could be directly linked to the sport, there are no doubt some fighters who, in a world like let's say, Mortal Kombat, could end the lives of their opponents in brutal fashion. They may not be able to pluck somebody's head (spinal cord intact) off their body, but they could come pretty damn close.

In honour of my tremendous temptation to run out and buy an Xbox One and a copy of Mortal Kombat X, I'm writing a list of the top 20 most brutal fighters in MMA history. Keep in mind though, that this isn't a list based off the best knockout artists. There are several fighters that, as this list will show, can be simply brutal without necessarily having any KO power. Submission artists are fully capable of inflicting tremendous pain on their opponents without rocketing a shoryuken to their jaw (wrong game series, I know).

Also, I'm not putting any limitations on where the competitors have fought to qualify. This will result in some names that may not be recognizable to the casual fan, but are still incredible brutal fighters who have to be mentioned on the list. And now without further delay, I present the top 20 most brutal MMA fighters of all time.

21 (Dis?)Honourable Mention: Keith Hackney

Anybody who wins a fight via groin strikes needs to be mentioned had he done something more with his career, he'd be higher up here.

20 20. Chris Leben

Not only is this man brutal, but he could also withstand a ton of brutality back in his day. As a member of the original Ultimate Fighter cast, "The Crippler" will always hold a special spot in Uncle Dana's heart for saving his company. It also helps that he possessed one punch knockout power and a chin forged in a Weapon X laboratory. His best moment though? His comeback KO of Terry Martin, which he went from a zombie back into a warrior to drop Martin for the win. Had Leben spent more dealing punishment than taking it, he would find himself higher on the list.

19 19. Mauricio Rua

Trained in one of the most infamous MMA gyms ever (Chute Boxe Academy), "Shogun" made his name in the PRIDE promotion by mauling his opponents with a super aggressive and varied Muay Thai attack. While not as reckless as some of his other Chute Boxe teammates (who may make an appearance later on) Rua made up for it with more technical skill. His knees may be blown to hell now, but fans sometimes still get a glimpse of the warlord who took out Quinton Jackson with soccer kicks in Japan.

18 18. Junior Dos Santos

Moving right along with another Brazillian, Junior Dos Santos was a virtually unknown fighter when he made his debut at UFC 90 opposite Brazillian Jiu-Jitsu world champion Fabricio Werdum. JDS made the world recognize his name though once he floored Werdum with an uppercut straight out of hell. Since then, Dos Santos has victimized men like Shane Carwin, Gabriel Gonzaga and Roy Nelson with his terrifying hand power. Should he ever receive another title shot, everyone should know that he is only one shot away from destroying the champion.

17 17. Edson Barboza

Can somebody please tell Mr. Barboza that lightweights aren't supposed to possess this insane amount of power? A kickboxer with one of the most spectacular knockouts you'll ever see, Barboza is up there with Anthony Pettis for having the best kicks in the lightweight division. What makes Barboza so brutal is that his kicks can nail you anywhere, he has recorded (T)KOs with leg, body and head kicks. By the way, a match up between Pettis and Barboza? Make it happen Joe Silva!

16 16. Masakazu Imanari

Leg locks are considered the most dangerous of submission holds, which is why they're banned in several grappling tournaments. So what happens when there is a fighter whose nickname means 'Master of Leg Locks'? Madness, that's what. Masakazu Imanari doesn't possess much in the way of a striking game, instead his gameplan for every fight is simply to massacre the legs of any opponent he faces. His record isn't perfect and he probably will never leave Japan, but make no mistake, Imanari is a dangerous "Ashikan Judan".

15 15. Vitor Belfort

I don't know what's in Brazilian water that turns their fighters into ferocious strikers, but I want some of it. "The Phenom" has had a roller coaster of a career but one thing that has remained constant is his penchant for absolutely brutal striking. From his blitz of Wanderlei Silva back at UFC Ultimate Brazil or his uppercut which lifted Dan Henderson off his feet at UFC Fight Night 32, Belfort's finishing ability has been witnessed by nearly every fan, new and old. If this old lion can harness some of his signature fury at UFC 187 (that is if it doesn't get postponed for the millionth time), I worry for the head of Chris Weidman.

14 14. Chuck Liddell

What is there that I could say about "The Iceman" which hasn't been said already, hell his name is proof enough that he's a stone cold killer! Liddell didn't like to mess around with the groundwork of MMA at all, instead he trained to be as exciting as he could be to mass audiences and it paid off big time. Liddell's striking power and unparalleled killer instinct was integral to the UFC's break into the mainstream back in the mid 2000s and few have come close to the ferocity Liddell displayed in his two fights with Tito Ortiz and his mauling of Vernon White. His chin prevented the warrior from doing his thing later in his career but the legacy of this iceman shall never melt away.

13 13. Ronda Rousey

Oh yes, she's more than a pretty face. Ronda Rousey is an unstoppable force of nature which has devoured every victim pitted in the octagon with her. While she hasn't defeated as many legends as some fighters on the list, Rousey's brutality is too violent to ignore. Her Judo background grants her with the best armbar in the game, an armbar which most famously snapped the arm of Miesha Tate back in their first encounter at StrikeForce: Tate vs Rousey. If Rousey keeps on this path, who knows where she will stack on this list once her career wraps up.

12 12. Shinya Aoki

Another Japanese name which many casuals will fail to recognize, the list of lightweights who can compare with the grappling of Shinya Aoki. Also known as Tobikan Judan (Master of Flying Submissions), Aoki has almost exclusively fought in Japan, but his body of work should terrify potential opponents all across the world. His flexibility allows him to contort his body into a million different ways, all of which hurt his opponent. His shining moment of brutality however came when he snapped Mizuto Hirota's arm with a hammerlock back in 2009 and taunted his wounded opponent. Damn, never has a man with rainbow pants been so frightening.

11 11. Quinton Jackson

If not for his notoriously problematic behaviour, "Rampage" would be a MMA promoter's dream. A power puncher who isn't afraid to say what's on his mind, Jackson was possibly the most popular American fighter in the history of the PRIDE organization. Younger fans may not be able to tell because of his current limited skill set, but Rampage was at one time known for his crippling slams just as much as he was known for his hellish hooks which he has used to knockout Chuck Liddell and Wanderlei Silva.  No matter where Rampage ends up once his current court case with Bellator is settled, know that Jackson is still has palpable knockout power in both hands or as Jackson calls them, his bungalows.

10 10. Fedor Emelianenko 

By far the greatest fighter to never strap on a pair of UFC gloves, all UFC heavyweights should consider themselves lucky that they never had to face "The Last Emperor" when he was at the peak of his powers in PRIDE. Even when Emelianenko couldn't land the decisive knockout shot versus men like Antonio Rodrigo Nogueira, he still thumped on them for what seemed like an eternity. The scariest part about fighting Emelianenko is that no matter where the fight was taking place, you were ALWAYS in danger of being finished. He doesn't possess as many clean KOs as others on the list, but his list of prolonged beatings and bone-crunching armbars is plenty brutal to qualify him on the list.

9 9. Dan Henderson

Holding the honour of being the last man to defeat Fedor Emelianenko, Dan Henderson is no doubt one of the most brutal fighters ever. He began his career simply as a wrestler, but he really made his name known based off one attack: the H-Bomb. It's a disservice to just call the punch an overhand right; the punch is so devastating that even in the twilight of his career it is still a danger for any fighter on earth. The pinnacle of his Dan Henderson's brutality came at UFC 100 when after shutting Michael Bisping's lights off with a H-Bomb, he dropped a forearm which rattled Bisping's ancestors due to its power. He may be a one trick pony at this point of his career, but what a hell of a trick it is.

8 8. Melvin Manhoef

The final fighter to never compete in the UFC is none other than Muay Thai wrecking machine Melvin Manhoef. Put simply, there is only one speed that Manhoef fights at: full clip. Lacking any sort of sophisticated ground game, Manhoef's best shot at victory is always to blitz his opponent with murderous leg and body kicks and punching flurries which would make video game characters jealous. His power and agression is so ridiculous that in 2008 he knocked out the adamantium laced heavyweight and former K-1 champion Mark Hunt as a middleweight in 18 seconds. Tip of advice to all of Manhoef's opponents; just take him down, for your own sake.

7 7. Cain Velasquez

When he's not out with an injury, Cain (no nickname needed) Velasquez is a goddamn nightmare for any UFC heavyweight. It's bad enough that heavyweights carry the most power out of any weight class, but Velasquez also has the gas tank of a fit middleweight which allows him to go deep into later rounds when all other heavyweights are gasping for air.

His knockouts over Brock Lesnar and Antonio Rodrigo Nogueira are brutal enough, but his second and third fights with former champ Junior Dos Santos are the ones you want to scare your friends with. If you look up bloodbath in a dictionary, you would find a picture of a wounded and concussed Dos Santos standing up only because Velasquez' punches are keeping him propped up on the fence. The pace and power of Velasquez will keep near the top of this list for years to come.

6 6. Mark Coleman

Any mixed martial artist who used a ground strike owes some part of their success, however minuscule to the Godfather of Ground n' Pound, Mark Coleman. A former Olympic wrestler who combined his blasting double leg takedowns with a healthy dose of headbutts, forearms, punches and knees (only in Japan) to massacre outmatched heavyweights in the early days of the sport. As the sport evolved, Coleman's strategy began to become outdated but in the late 90s and early 00s, few heavyweights inspired more fear in the opponents than Mark Coleman.

5 5. Rousimar Palhares

Earlier on this list, I wrote that Masakazu Imanari's nickname was the master of leg locks. If that's the case, then Imanari has stiff competition for that distinction in the form of "Toquinho" Rousimar Palhares. The only way one could describe Palhares is to imagine a completely unrestrained version of Imanari manifested itself in a Brazillian man's body.  Seriously look at him, would you want that guy anywhere near your leg?

Palhares latches on opponents' legs like a dog on a bone and snaps their legs even as the referee tries to pull him off. Suffering a knockout is life altering for sure, but the brutal pain of a heel hook is something that you should only wish on your worst enemies. The fact that the heel hook is his calling card is fitting; only a brutal fighter like Palhares can claim that technique as his own.

4 4. Alistair Overeem

He may be going by his "Reem" nickname now, but "The Demolition Man" is a much more fitting moniker for this Dutch menace. Once a gangly light-heavyweight, Alistair Overeem as a heavyweight now looks more monster than man (thanks in part to ahem, "horse meat"). In addition to his ridiculous physique, Overeem also possesses some of the hardest hitting strikes in all of MMA and in particular his knees, which have knocked out the indestructible Kazuyuki Fujita and massacred Travis Browne in the opening minutes of their fight. His durability has been called into question several times, but when he's dishing out the offence, stay the hell out of Overeem's path.

3 3. Cristiane Justino 

I don't care that a new Terminator movie is coming out. For my money, Cristiane "Cyborg" Justino is the only cyborg worth talking about in 2015. Undoubtedly the most fearsome striker in all of Women's MMA, Justino doesn't defeat her opponents, she massacres them.

After losing just once in her debut, Cyborg has not looked back, smashing every single challenger that has come her way in her ten year career. The speed of which she pounces on her opponents is a sight to behold and her physical strength is unparalleled with any other woman fighter. Her only potential challenger, Ronda Rousey, lies outside of her  home in the all-female promotion Invicta FC. Should Cyborg manage to cut her weight down to 135 pounds, it's practically a guarantee that MMA fans will see a superfight between the two greatest WMMA fighters of all time.

2 2. Mirko Cro Cop

Right kick hospital, left kick cemetery, do I have to say more? This former Special Forces officer (yes Cro Cop isn't just a gimmick) plied his trade on the kickboxing circuit for years before entering the world and MMA and I'm sure his opponents wished he would have stayed there.

At his peak in PRIDE, Cro Cop was considered the deadliest striker in the world as his combination of left kicks and left straight punches made him a fan favourite to all. Whether it was destroying the mythical creature known as Bob Sapp's orbital bone or laying out the stone cold Igor Vovchanchyn with a single kick, Cro Cop's brutality knows no limits. The crazy part is that Cro Cop seems like a super chill guy- could you imagine if he wasn't? Oh please let's not, I'm already getting scared.