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Introduction
Here we have Rock Lee vs Gaara. This was an extraordinary fight, one of anime's best for many. However, it's obvious the amazing factor of this fight came from Rock Lee. Gaara had his moments, but this wasn't one of them. In fact, in my opinion, Rock Lee should've won... I mean he REALLY should've won. Allow me to show that Gaara's win was due to Plot-No-Jutsu. And do read... it should be entertaining!
1. Plot-No-Jutsu Style: Worst-Possible-Match-Up Jutsu!
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I know this technically isn't PNJ, but it's worth mentioning. There were 20 contestants. TWENTY OF THEM. What are the chances then, of the singular Taijutsu using Ninja to go up against a Jinchuriki who had murdered several Jonin level and less ninja in his time, as well as never being TOUCHED in his life. MC Hammer was his role model.
Gaara was literally the absolute worst possible foe for Rock Lee. Sure, Gaara's undoubtedly difficult for anyone else... but let's be real. If Rock Lee went up against ANY other of the other 18 contestants, it would've been a certain victory. Rock Lee had to go up against the a Jinchuriki who's fighting style happened to be the perfect counter against his own. In essence, you had Rock Lee not only going up against an extremely skilled/talented/powerful opponent, but also someone who has a perfect fighting style for countering Lee's, that none of the Ninja's had. Really Kishimoto?
2. Plot-Style: Impossible-Clone-Creation Jutsu!
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We know that during the fight, Rock Lee's original state isn't enough for the bad-luck-match-up. So he turns up. Off goes his weights, on goes his speed. At this point, people eyes can't keep up with Rock Lee's speed... and neither can Gaara's sand.
With a sudden burst of incredible speed, Rock Lee blitzes Gaara, knocking him into the air. While kicking him up, we know Rock Lee winces for moment, and in that moment Gaara creates a clone. Rock unknowingly then proceeds to Primary Lotus the clone instead, sparing Gaara and putting Lee in a state of needed recovery.
Now this just doesn't sit well with me, and my friend common sense agrees. Let me list why:
A) LOOK AT THE SCAN. THE DUDES SAND IS BEHIND HIM! HOW DOES HE MAKE A CLONE! Now, some may make the excuse that it came from his sand armor. As silly as that sounds, let's assume that.
Frankly, it doesn't matter even if he did have sand, because B) HE'S GETTING FREAKING UPPERCUT REPEATEDLY WITH A MULTITUDE OF FEET. Looking at the scans and anime, he's not even done flinching before the next kick connects. How then does he make a clone?
No more than you can do origami and MMA at the same time, should Gaara be able to create a clone of meager sand while getting kicked in less than a second intervals. Gaara obviously would've needed some of the sand to get him back on the ground anyway. So we're supposed to believe that in less than 1 second, Gaara flinched and recovered from a gravity-defying kicks, molded chakra (which mind you is being used to try to catch up his sand under him), calculate and remove enough sand to make a clone and enough to take him to the ground, actually remove himself, replace himself exactly with a clone, and descend out of Rock Lee's sight. Such would be an impressive feat for the likes of Shikamaru, Minato, and Sauske. How the heck could GAARA- no, GENIN GAARA do such a thing? Plot chakra, that's how.
3. Plot-style: I-Don't-Die-When-I-Should-Ha-Ha
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After this, Rock Lee, being wiped, resorts to his gates, fighting in the 4th, and ending with the 5th. 3-Tamoe Shargian/Byakugan were having trouble / couldn't keep up or see him. Kakashi even for goodness' sake. This sort of speed leaves the world of ninja and reaches that of superhero. I mean this is crazy. Not just the speed but the utter raw strength such gates provide... it's amazing.. awing... Jonin level, and when used to it's full potential, far above. This Lee is a few seconds made the no-weights Lee seem childlike. Yet base Lee with a simple hard punch could break a large part of Gaara's sand armor off. Now, if that's the case, explain to me HOW THE HECK A BAJILLION PUNCHES WITHIN THE MATTER OF A FEW SECONDS DELIVERED WITH POWER THAT WOULD MAKE FALCON PROUD, ENHANCED BY THE SPEED OF HIS MOVEMENT, NOT DESTROY ANY SHRED OF ARMOR!
I mean let's be reasonable. Rock Lee evidently became many times stronger than normal. Not 10. Not 20. Not 30. I mean, to be frank, I don't know the number... but I don't think saying +50 times normal power would be a stretch. Maybe ~100. He went from an easily traceable upper kick combo of a few hits to an unseeable frenzy of complete and utter destructive blows happening multiple times- no -many- times every second with an exponential strength growth tossed in, mixed with, lastly, the inherent direct impact boost anything will gain with additional speed applied. This, my friends, is what we refer to as "swag". Yet, with a plot-shield stronger than his sand one, Gaara protects himself almost if not completely from every blow, when just ONE of those punches would end the fights for any other contestant. At best 2 or 3. It doesn't any sense that a base mode punch can destroy a large portion, and 4th gate repeated blows do less damage to his armor, and don't even damage Gaara himself.
And let's not forget that last blow. A 5th gate punch, with all his strength, direct, point-plank, explosive power, to an already wrecked damage sand armor. HOW DID THAT NOT KILL HIM? I'd rather hit that concrete that get hit by that fist. Heck, the concrete would be several times preferable to the repeated 4th gate blows, even individually. That one punch was enough to destroy any illogical armor Gaara still had and, to be frank, eradicate him then and there, BEFORE EVEN HITTING THE GROUND. That punch was far more harmful than some still concrete.
Lastly, even if he did survive all that without a scratch to his body, having a little bit of sand under him shouldn't save him from anything- at least not logically. We already know his sand couldn't keep up, so it literally could just become sand- it doesn't have time to catch him, cushion him, or in any way be manipulated. It's solely just a few pounds of sand laying behind him without time to do anything useful. Yet, of course, Gaara's plot-shield wasn't pierced.
Conclusion
So we know at the end of all this, Gaara's plot-shield prevails, and sadly Rock Lee (who was leagues ahead of the other Genin) lost then and there. Due to a horrid match-up, impossible clone jutsu use, and Gaara gaining an apparent temporary invulnerability, Rock Lee lost what I believe he should've won. Oh well.