Orochimaru was the leader of the Sound Village and the strongest antagonist at the beginning of the Naruto series. He was infamous for his unapologetically malicious behavior and for the pernicious way he had inducted Sasuke Uchiha into his service.
At first, it seemed as if the shinobi was a flawless force for evil. However, as time elapsed, the anime has illustrated that he suffers from many crippling flaws both as a fighter and as a person. The contrast between his most prodigious shortcomings and his strengths illustrates the complexity of his character.
10 Weakness: as the series & its characters progressed, the Sannin's strength only diminished
Compared to the characters introduced at the beginning of the series, Orochimaru was stronger than most (save for a handful of individuals such as Might Guy or Sarutobi). The improvements he made to his own body were greatly conducive to the power at his disposal.
However, as the series and its characters progressed, the Sannin's strength only diminished (since the Third Hokage took his arms after their fateful fight against one another). By the time he was restored at the end of the Fourth Great Ninja War, both Naruto and Sasuke had surpassed him beyond his wildest dreams.
9 Strength: the unparalleled intelligence at his disposal is the reason he was able to survive through the original series & Shippuden
One of Orochimaru's greatest strengths (and the reason he was able to survive not only through the original series but also through Shippuden) was the unparalleled intelligence at his disposal.
In addition to discovering immortality (through inhabiting different bodies and gaining the powers of his previous hosts), he was also able to scientifically augment his minions. This made them significantly more deadly when they inevitably faced the heroes, with some antagonists strong enough to defeat Rock Lee in spite of his taijutsu prowess.
8 Weakness: Despite Orochimaru's intelligence, his schemes often lack foresight
An example of his lack of foresight can be discerned through his battle against Jiraiya and Tsunade after the latter had refused to heal his arms. Though attempting to bribe her may not have been an efficient strategy, killing her outright would have yielded much poorer results.
Further, he was unprepared for the possibility that Sasuke might one day turn on him, betraying their deal as he pursued his revenge. Ironically, the fallen Sannin had unwittingly provided his new pupil the very tools that would procure his own demise. From what is perceivable, most of his long-term planning ability leaves much to be desired.
7 Strength: his leadership skills are superb
Despite Orochimaru's poor foresight, his leadership skills are superb. He was able to gauge the strengths of the Sound Four, sending them on dozens of successful missions before the attack on Konoha (some of which were even S-rank).
When it became time for him to confront Sarutobi, his servants constructed a ward around the arena, efficiently sealing off any intruders who would attempt to breach the barrier from the outside. Similarly, the team he commanded would successfully retrieve Sasuke — even if the avenger was the only member of the group to return from the Leaf alive.
6 Weakness: Orochimaru's lack of empathy was one of his primary reasons for turning away from the Leaf & becoming a fugitive
His lack of empathy also debilitated his success on many of his missions, even among his Sannin comrades. When the Stone surrounded a mountain from all sides and began to cave it in, Orochimaru wanted to "mercifully" kill Jiraiya so that he would not be captured by the enemy.
Given that their salvation was only moments away, taking the sage's life would have been a massive mistake and one Tsunade never would have forgiven him for.
5 Strength: While Orochimaru may not be the most subtle, he is nonetheless a master manipulator
He was able to sway Sasuke to his side not by kidnapping him, but by demonstrating how the strength that Konoha offered was insufficient. This prompted his prospect to leave on his own record and even fight against those who tried to retrieve him.
The Sannin was equally proficient at finessing Naruto himself. He was not explicitly punished for his crimes on account of what service he provided at the end of the Fourth War. However, this is in spite of the fact that he only resurrected the Hokage because Sasuke forced him to.
4 Weakness: Orochimaru's restlessness was one of his greatest flaws & part of what prompted him to take action against the Leaf
He wasn't explicitly seeking vengeance for being hunted by them on account of his experiments. Instead, he wanted to cause as much chaos as possible to get things in motion and to satiate his sadistic tendencies.
Poetically, the havoc he caused would paint a massive target on his back and disrupt his research, as many of Konoha's finest were investigating his laboratories and forcing him to vacate them.
3 Strength: Orochimaru's versatility makes him an unpredictable & deadly ninja
He is able to unleash snakes in any incarnation and is a deceptively skilled martial combatant to compliment his affinity with ninjutsu (proven through his fight against Log).
When necessary, the man is capable of retreating or otherwise escaping from perilous situations. This was particularly evident through his narrow obviation of Itachi Uchiha — should he not have brought Kabuto along to intervene, the Akatsuki member would have ended him for his treachery.
2 Weakness: his Mortality — the closer he comes to his body's expiration date, the weaker the Sannin becomes
While his ability to transfer his souls between bodies grants Orochimaru an excellent boon in power, it comes at an arguably even greater expense. Every three years, he is forced to find a new host since the form he currently resides in begins to fall apart and forcibly reject him.
If he is unable to locate a new vessel strong enough to contain his power, he is destined to perish. Further, the closer he comes to his body's expiration date, the weaker the Sannin becomes — a fact that Sasuke realized and was elated to capitalize on.
1 Strength: Orochimaru's greatest strength is handily his tenacity
He was the only villain to have survived from the beginning of Naruto through the end of Shippuden (aside from Kabuto), persisting through dozens of brushes with death.
The most obvious example can be gleaned after he was slain by Sasuke, only to be reborn through the curse mark he had placed on Anko's neck many years later. There was a similar design embedded on the young Uchiha, though it was destroyed during his battle against Itachi. Orochimaru is evidently able to escape from any inhibition — whether through his insidious reputation or the powerful foes who seek his head — no matter how insurmountable the obstacle might seem.