The Chunin Exams were one of Naruto's earliest and most memorable arcs. Not only would it introduce many of its staple characters (heroes and villains alike), it was an excellent showcase to the jutsu they were capable of and a reference point for their power going forward.
Despite the insurances Konoha took to secure the sanctity of the test, it was one rife with evildoers. By ranking the antagonists on a basis of their power, we gain a fuller understanding of the threat the Leaf faced, as well as an appreciation for the heroes who were able to halt it.
10 Kin
Kin was a member of Dosu's team and handily the weakest among them. She had the ability to throw needles with bells on them at her targets, ones which would cause a disorienting resonance after they had jingled together.
The combination of projectiles with and without bells aimed to distract her foes and throw them off from the full scope of her attacks. However, since Shikamaru was quickly able to deduce the nature of her skills, he defeated her with minimal effort.
9 Yoroi
Yoroi was one of Orochimaru's minions and a man intent on drawing out Sasuke's curse mark. He fought against him in the first round of the tournament, narrowly losing to the applied might of the young Uchiha's default jutsu (such as his fire style and Lion's Barrage).
Able to infuse his fists with chakra, he posed a considerably greater risk to his opponent than Kin did to hers. His striking power necessitates that his foes must keep their distance and remain wary, as he is able to dispatch them expediently if they come within his rapacious reach.
8 Baki
Baki was the mentor to Gaara and a man with deceptive skill. Though he did not have the flashy jutsu of his students (such as Temari's fan or the Jinchuriki's sand coffin), his wind blade was a treacherous force to be reckoned with. It was just as sharp as steel and able to permeate through physical objects.
As a result, he managed to cut down Hayate Gekko, the Chunin Exams' proctor, before the clandestine pact between the Sand and Sound villages was revealed. In spite of his opponents' dizzying speed, he could not parry an attack that phased through his weapon.
7 Zaku
Zaku was a close friend to Dosu and one of the strongest early shinobi that Team Seven fought against. After their brush with Orochimaru, none of them were able to withstand the immense sound he could emit from his hands. At the height of his power, he could unleash a devastating shockwave that impacted everyone in front of him.
However, Shino realized that his jutsu was only applicable on account of the modifications to his corporeal body. During their battle against each other in the tournament, he used bugs to infiltrate the pipes in his arms, causing them to burst and defeating him utterly.
6 Kabuto
At the time of the Chunin Exam, Kabuto was only a moderately skilled shinobi with an extremely limited arsenal. His primary weapon was his ability to concentrate his chakra into scalpels, ones that could cut through muscle and bone more fluidly than any physical sword.
To compliment it, he also had immense medical ninjutsu training to heal whatever injuries he incurred in his service to Lord Orochimaru. With these skills, he was able to narrowly survive a brush with Kakashi Hatake, escaping him after he had failed to assassinate Sasuke in the hospital.
5 Kankuro
When he was introduced, Kankuro was exponentially more villainous than later in the series. He threatened to attack Konohamaru and constantly instigated conflict with the members of the Leaf. The puppets at his command were deadly and unique, each fitting dozens of weapons into hidden compartments that could kill their targets by exposing them to the poison on their tips.
As skilled as the doll master might be, there are fundamental weaknesses that can be exploited by an intelligent opponent. Not only is he terrible at taijutsu, severing the chakra threads connected to his creations will inhibit his access to them. This was a fact that Shino exploited during their forest battle.
4 Dosu
Dosu may have faced an undignified death at the hand of Gaara, but his skills entailed his success against most of the opponents he might encounter. The gauntlet on his arm was able to produce a pressurized sound that could track its target and was impossible to block.
Moreover, his attacks disoriented the senses of his opponents and put them in a state of vertigo. Subsequently, it makes attempting to attack him with projectiles difficult and melee ill-advised.
3 Temari
Temari was Gaara's sister and decisively one of the most powerful kunocihi in the original series. A single sweep of her fan could knock back opponents, scattering weapons and slicing open their skin as if it were paper.
This makes it incredibly perilous to fight her since her weakness in melee combat is nearly impossible to exploit (because those who attempt to approach her are merely blown back). Fortunately, Shikamaru was able to outsmart her in their match, paralyzing the woman and preventing access to her harrowing weapon. Despite his hard-won victory, he would forfeit anyway - much to everyone's shock and disappointment.
2 Gaara
Gaara was the most powerful member of the Sand Village during the Chunin Exams and its secret weapon against Konoha. In addition to the Jinchuriki in his possession—one whose massive size rivaled that of the stolid Gamabunta—the particles in his command were infused with the soul of his mother.
As a result, he was able to defend himself in many of his battles without lifting a finger or even consciously attempting to block his opponents. He would finally face injury (and nearly defeat) against Rock Lee, narrowly overcoming him after the taijutsu expert had exhausted his body.
1 Orochimaru
The mastermind behind the invasion of Konoha, Orochimaru's objective was to cause as much destruction and pain as conceivably possible - ideally, bringing an end to the Leaf. Acknowledging that Sarutobi might be too powerful for him even in spite of his old age, the fallen Sannin came prepared with the Edo Tensei resurrections of the First, Second, and Fourth Hokage—though the latter was botched before it could be completed.
While his plans may have been foiled and his body broken, the pernicious effects of his actions were felt by Konoha for many years to come, especially through the loss of their beloved leader.