Spock was a linchpin character that helped define Star Trek and everything that followed. He was the half-human/half-alien who helped bridge the audience's gap between worlds and sell the franchise's message of exploration, unity, and knowledge. His character traits were strong, and they made Spock what he was in the minds of Trekkers the world over.
As a Vulcan dedicated to the pure pursuit of logic, Spock was bound to step on a few toes when dealing with other races and shipmates. Yet, he stuck to many of these character traits until the very end, and it helped turn him into a cultural icon within the ranks of not just Starfleet, but countless other galactic worlds.
His Devotion To Logic
Vulcans view logic as the ultimate form of existence, and a lot of this can be traced back to their early history as a violent, passionate race. It almost became their undoing, which is why the Vulcan culture adopted a religious philosophy of pure logic. Many viewed this as a pendulum shift in the opposite extreme direction, and there was merit to that claim.
Spock might have used emotion to save the day, but he was determined to live a path of logic, just like any other Vulcan. However, that was especially difficult, given his half-human bloodline. Still, he was determined to complete the ritual known as Kolinahr, the purging of all emotions from the mind, to attain a state of pure, unadulterated logic.
His Arrogance
Vulcans were widely regarded by many species besides just humans as being arrogant and boastful. Indeed, a lot of this had to do with Vulcan culture, which did place a lot of emphasis on logic, while nitpicking the flaws of other cultures who didn't think as they did.
Spock was no exception. While he was careful not to alienate people on purpose, Spock had real trouble being humble, and that turned off a lot of people. Had he exercised a bit more finesse, he may have attracted more to his side.
His Sarcasm
Spock was not quite the soulless automaton that many considered him to be, and part of that might have had something to do with his split half-human heritage. While "logical" in itself, his sarcasm was pointed and effective. He'd often use it to discourage his enemies and gain the upper hand.
Other times, his sarcasm stemmed from frustration with those around him. Though he went through life missing many a joke, Spock was nevertheless capable of giving as good as he got... at least in his way.
His Banter With Dr. McCoy
One of Spock's most entertaining character traits was his incessant banter with Dr. McCoy, whom he viewed as both a close friend and a frustrating rival. Indeed, McCoy hated much of what Spock stood for, particularly his seeming nonchalant ambivalence towards matters of great importance.
The two would exchange humorous barbs designed to insult one another, but it was usually Spock who landed the heftier blows. In truth, Spock may have enjoyed all the banter as a means of bonding with his crewmate. After all, Spock did bestow his consciousness on McCoy, shortly before he died in Star Trek II: The Wrath of Khan.
His Loyalty To Captain Kirk
While Spock was loyal to the mission, first and foremost, he often put this behind him wherever Captain Kirk was concerned. His loyalty to the Captain was meme-worthy, even in times of great disagreement. This was especially odd, given Captain Kirk's inherent emotional passion, which Spock often regarded as illogical, and counterproductive.
Spock saw something in Kirk that others missed. While many in Starfleet viewed him as a prime candidate for the position of Admiral, Spock realized that his first, and greatest strength was that of a starship Captain. In his own words, "Anything else is a waste of material."
His Insatiable Curiosity
The mysteries of science and space have long fascinated Spock, which is one of the reasons he entered Starfleet, much to the chagrin of his father. As a science officer on board the Enterprise, Spock was optimally suited to discover strange new worlds and civilizations.
When the dangerous V'ger entered Federation space, Spock could not resist the urge to mind-meld with it, in an attempt to learn about its awe-inspiring creation. It was through Spock that the Enterprise crew learned what they were dealing with, and were able to properly broker peace with it.
His Compassion
Spock's logic isn't quite as cold as many people think, and he's demonstrated this over and over again. While he does agree with certain philosophical claims, such as "the needs of the many outweigh the needs of the few," he never looks at any race or people from the point of view of a numbers game.
It was Spock himself who suggested that the Federation open up diplomatic relations with the highly influential Klingon Chancellor Gorkon, following the disaster on the moon Praxis, near their homeworld. This, despite massive hostilities between the two, and the desire of many in Starfleet to see the Empire brought to its knees.
His Diplomatic Personality
Spock may view emotion as an obstacle in the path of greatness, but that hasn't stopped him from being an effective diplomat. It's yet another trait he shares with his father Sarek, a man who has presided over multiple diplomatic missions throughout his time within the Federation.
While not as renowned as his father, Spock made a name for himself as a diplomat, often by bucking established trends and norms. For instance, he traveled to Romulus in his quest to reunite the Vulcans and the Romulan people, even at the cost of looking like a traitor to the Federation.
His Intelligence
Spock is extremely gifted in terms of intelligence, and knowledge. His mind is purely scientific, and he applies that knowledge in ways that benefit not just the Federation, but other worlds as well, including hostile ones. Spock views science as a tool for the betterment of all, and he's honed his mind in preparation.
Whether it's a scientific theory, mathematical excellence, or the highest echelon of philosophy, Spock is stuffed to the brim with knowledge. He has been shown to get along well with Lieutenant Commander Data, as the two are quite similar in many respects, including this one.
His Charisma
As far as Vulcans go, Spock is one of the most charismatic, a trait he may have inherited from his father, the legendary Sarek. Though half-human, Spock is arguably more Vulcan in almost every way, and as such, he can't rely on his human side to help him win friends or the respect of others.
Yet, Spock's combination of character traits helped propel this one to the forefront. He's widely regarded across many worlds as being one of the most charismatic Starfleet officers in history, and his confident, stalwart personality probably has a lot to do with it.