CANON HISTORY: praise the lord for this wiki link
CANON PERSONALITY:

Roronoa Zoro is a five hour energy shoved inside a bulk supply of protein shakes shoved in the closet of the sweatiest, nastiest bodybuilding gym in the world. He's a pirate, a thug and a wannabe samurai who lacks the morals generally required to be a hero. Amongst the main cast, he’s the the cliche tough guy: gruff, reserved and stern. The "Cool" one that always talks about keeps a level head when the pressure is on, who stares death in the face without a hint of fear. He's the cocky jock of the Strawhat Pirates; the unaffected, antagonistic brute who matches oncoming hostility with arrogant irreverence.

Yet, he's also the one who can't tell left from right. The one who needs to be babysat when left to wander or else he'll wind up (no joke) stuck upside-down in a chimney. He's gruff, yet frequently plays the protective older brother to his youngest crewmate, Chopper. One of the more mature on the crew and yet still thought it was a great idea to put a king and his entire court in chains. He'll keep a level-head until some coincidental resemblance to his dead best friend makes him regress to five-year-old behavior.

Basically, for every "cool" moment of Zoro's, there's two instances of him being a complete moron. One would think this would negate all his smooth one-liners and impressive moments and it does, but only for some. The rest are left unscathed, protected by the conviction that Zoro places behind every action.

Zoro's ambitious. His determination to fulfill his dream is one of the main components of his character. He will become the best swordsman in the world or he will die. Literally. He's more than willing to kill himself trying to reach the top. To Zoro death is simply proof that he wasn't strong enough to achieve his dream; a sure sign that he was weak not only in body but also in mind.

For Zoro, becoming the best swordsman doesn't just involve physical ability. To become the best he has to have the mentality of the best--clarity of mind, dauntless spirit and, most importantly, strong conviction. A swordsman's words are his actions. They live without regretting the past in order to keep themselves grounded in the present as they look on towards the future. At least, that's what Zoro believes. As a result, he stands behind every decision he makes, taking the rewards along with the consequences and learning from both. One instance of this is when he tasted defeat at the hands of Hawkeye Mihawk. At the time he was overconfident, believing himself to be untouchable and underestimating the difficulty of his dream. Mihawk's victory over him humbled and humiliated him but it also lit a fire. Zoro vowed never to lose again and up until current canon has made good on that promise, pushing through every fight no matter how much the odds were stacked against him.

Well, mostly.

See, another signature moment for Zoro is his confrontation with Bartholomew Kuma during the Thriller Bark arc. Kuma, a powerful ex-pirate turned government dog, came to Thriller Bark in order to retrieve an injured Luffy. While everyone was wiped out, Zoro fought through fatigue and injury to protect his captain, going so far as to offer his head as a replacement for Luffy's. Considering his drive to accomplish his dream, the request was a bizarre one until he explained his reasoning. He had signed on to be Luffy's first mate and support his goal to become the pirate king. That was his duty now. If he failed that, how could he possibly manage to become the best swordsman?

It's a weird way of thinking. At first it even seems nonsensical. But take into account this: Zoro follows a bushido-esque code that emphasizes things like integrity, honor, duty and loyalty. Similar to his concept of a swordsman's conviction, failing any of these traits would be failing as both a swordsman and a man.

Zoro is extremely protective of his crew and takes his duty as first mate seriously. When a crew member needs help he'll be there and is often seen protecting the "weaker" members of the crew--most notably Chopper. While his job may not be to unify the crew, it is to support the captain and watch over the rest of the crew when Luffy's unable. Therefore it can be said that one of his greatest fears is not being strong enough to protect them, something he never thought possible until Kuma returned.

Using his ability, Kuma separated the crew to different parts of the world where they remained separated for two years. Zoro, being gravely injured from his first encounter with Kuma, was the first one to go. For Zoro, it was a repeat of his loss to Mihawk and a glimpse of what awaited them ahead. It struck fear in him; one that he then used as motivation to improve his skills and resolve so that it would never happen again. Similarly, when the crew is reunited, he's the one to remind them to take their enemies seriously, knowing (and worried) that a cavalier attitude could destroy them all once again.

Yet when everything's said and done Zoro really isn't an angst-ridden guy. He's grumpy and kind of hostile towards strangers but in the end he's pretty relaxed. Simple things make him happy; alcohol and a good party, sunshine and a nice place to nap. He can even get distracted in situations that call for urgency, like in the Dressrossa arc when he abandons his urgent task in favor of watching gladiatorial fights on fake-TV. He's a serious guy but that doesn't necessarily mean he's uptight.

Or methodical. In fact, Zoro's a pretty reckless guy, particularly in a fight. He's bloodthirsty and battle-hungry to the point where he's actually said things like "my sword's been growling; it craves blood". He's no stoic samurai about fighting--it's his favorite past-time. He'll challenge anyone who looks strong enough to give him a fun fight that will inevitably leave him bleeding out. He's kind of a masochist like that. But hey, anything that'll make him stronger, right?

What a fucking weirdo.

SKILLS/ABILITIES:

Zoro's a shonen hero and has all the ridiculous skills and capabilities you'd expect a shonen hero to have. He's a really good swordsman. He can slice through iron and stone and send weird long-distance strikes from his sword sometimes. None of this is canonically considered a power.

Annoyingly, the way Zoro wields his swords is important to note. He has several styles of fighting that are pretty self-explanatory: one-sword style, two-sword style, and his infamous three-sword style where he places one sword in his mouth. Lastly he has possibly the weirdest, dumbest style called nine-sword style where he basically becomes the god Ashura except with nine arms instead of six and he grows another head. It's an illusion but the strikes manifest in reality. I think. Honestly, I'm not quite sure what's happening there.

He's also ridiculously strong. Once he lifted half of a building off of himself using his own two hands. He lifts like 800 million pound weights with two hands. This is also not considered a superpower even though it damn well should be.

As with all shonen heroes, he can magically jump the height of the empire state building and dodge bullets and whatnot. This unbelievable agility is also not considered a superpower.

The single thing that could be equated to a superpower is Haki. Haki is within every person at birth but must be awakened in order to be used. It is essentially the spiritual power of ambition that can be channeled for practical purposes. Zoro can use two types of Haki that can be used: Observation Haki (spiritual energy radar and sometimes precognitive abilities) and Armament Haki (using haki to create invisible armor aka a hardening method).

Unlisted anywhere is Zoro's remarkable blood bag ability. Somehow, he is impervious to blood loss. This is also unexplained and not considered a superpower.