Brock Lesnar's 5 Biggest Moments

Brock Lesnar has accomplished so much in his mixed martial arts career in a short amount of time.

In the two years since Lesnar made his UFC debut, he has made a huge impact on the sport of MMA. Since his debut, Lesnar has fought only the best competition that UFC has to offer. Collecting wins over Frank Mir, Randy Couture and Shane Carwin, Lesnar has arguably become the company's biggest draw.

Now, at 33 years old, Lesnar sits atop the heavyweight mountain with the UFC Heavyweight Championship intact—and shows no signs of giving it up.

Ahead of his anticipated clash with undefeated heavyweight prospect Cain Velasquez at UFC 121, we'll take a look at the moments that have defined Lesnar's career so far. From suffering defeat, to capturing UFC Heavyweight crown, it's not hard to see why Brock Lesnar is the baddest man on the planet.

No. 5: Lesnar Vs. Min Soo Kim

Lesnar vs. Min-Soo-Kim

Prior to joining UFC, Lesnar made his MMA debut under the K-1 promotion in Japan.

He squared off against Min Soo Kim and made short work of his opponent. Lesnar was nothing short of dominant, as he immediately took down the Korean kickboxer and began pounding on him. Lesnar used his sheer size to smother Soo Kim and easily passed his guard, securing a full-mount position.

From there, Lesnar unloaded punches to the head of Soo Kim and forced his opponent to tap due to strikes.

No. 4: Lesnar Vs. Shane Carwin

After battling a life-threatening illness, Lesnar made his highly anticipated return to the Octagon to defend his title against Shane Carwin at UFC 116.

Carwin was Lesnar's biggest opponent yet, matching up with the champion in size and strength.

In the first round both men took the center of the Octagon, and Carwin wasted no time trying to finish his opponent. Carwin blasted Lesnar with a right hand and followed up with an uppercut that rocked the champion. From there Carwin began to unload a vicious assault on his opponent and looked to be just moments away from securing the title from Lesnar. However, Lesnar somehow managed to survive the brutal ground-and pound from Carwin and retreated back to his feet to finish the round.

In the second round Carwin appeared tired, as he was breathing out of his mouth and holding his hands low. Lesnar took advantage and brought the fellow behemoth to the ground. Lesnar passed Carwin's guard and sunk in an arm-triangle choke for the win.

No. 3: Lesnar Vs. Frank Mir (1)

In 2008, Lesnar made his highly anticipated debut against veteran Frank Mir at UFC 81.

From the opening bell Lesnar dominated the experienced Mir, even though he wound up getting caught in a submission and losing the bout.

As both men began the first round, it took only six seconds for Lesnar to scoop Mir off his feet and plant him to the canvas. Lesnar proceeded to pound Mir's face in with a combination of strikes, but he accidently landed an illegal blow to the back of Mir's head, and the fight was forced to stand back up.

Once the action continued, Lesnar dropped Mir again, this time with a straight jab. Once again he proceeded to ground-and pound his opponent. From there, Lesnar gracefully spun around and took Mir's back and continued to land strikes. Mir attempted an armbar, but Lesnar escaped and continued to land hammer fists and elbows.

While he was in Mir's guard, Lesnar stood up. But he left his legs open, allowing Mir to elevate his hips, spin around and lock in a kneebar for the victory.

No. 2: Lesnar Vs. Frank Mir (2)

Lesnar and Mir would meet once again, this time to unify the UFC Heavyweight title at UFC 100.

Prior to the bout, there was a lot of trash-talking between the two heavyweights, and they showed a mutual disdain for one another.

In the first round, Lesnar took Mir down easily. But he was much more composed in Mir's guard, as he laid chest to chest and rarely exposed himself to a submission. Lesnar began to land hard shots to the body of Mir, passing his guard quite easily. Lesnar got into half guard and started landing strikes to the face of Mir, preventing him from gaining any movement. Lesnar held Mir in a neck wrench and continued to land shots.

When the first round came to a close, Mir's face was battered and bruised, and it was evident that Lesnar was not the same fighter Mir had fought before.

As the second round began, they briefly contested the bout on their feet, but Lesnar brought Mir to the ground again. Lesnar then used his massive frame to control Mir and began to land strikes to his face and body. As Lesnar beat up his opponent, the shots were becoming much more powerful and effective, and he eventually knocked out Mir in the second round.

No. 1: Lesnar Vs. Randy Couture

Despite the outcry from fans and critics, Lesnar earned a title shot against then-UFC Heavyweight Champion Randy Couture at UFC 91.

In the first round, Randy had the 265-pound challenger in the clinch, looking for a way to secure a position and control the big man.

It was no use.

Lesnar then went to shoot in on his opponent, with Couture stuffing the takedown. After jockeying for a position, Lesnar scooped Couture up and took him down.

On the ground it looked like the inexperience of Lesnar was about to show, as he almost gave his back to Couture. However, Lesnar picked Couture's ankle and took him to the ground once again.

As the round drew to a close, Couture landed a few good shots and again looked to clinch with the challenger, only for the bell to sound.

The second round opened up with both men trading shots and Lesnar getting the better of the two. He threw an elbow that wobbled Couture and seemed to have him hurt, but Couture again went back to the clinch.

Using his amateur wrestling skills, Couture tried to slam Lesnar, but the size alone was too much for him. Soon enough they went back to trading blows. Couture landed a shot that cut Lesnar right below his left eye, and it seemed the champion was determined to put Lesnar away.

However, a right hand to the temple rocked Couture, and Lesnar pounced on him immediately and won via TKO. In just his fourth MMA fight, Brock Lesnar was crowned UFC Heavyweight Champion.