Roronoa Zoro is one of the best swordsmen in One Piece. His reputation in battle is not an overestimation of his skills; in fact, to dance with his blade would mean almost certain death for most. Since the One Piece crew doesn't exactly fight Dungeons and Dragons monsters on normal voyages it is only speculation as to which ones Zoro could defeat and which ones would give him a run for his money.
Yet, through knowledge of his skills, a good estimate of his chances can be obtained.
10 Destroy: Abominable Yeti
A yeti would pose a serious threat to anyone who dared to face it, especially on its own terms and terrain. So when it comes to whether or not Zoro would stand a chance with it, one has to consider that a Yeti no matter how ferocious would be powerful yet slow.
The yeti's lack of speed almost assures that Zoro could slice it up with the utmost of ease due to his quick fighting style and ability to dodge the Abominable Yeti's fierce attacks.
9 Good Fight: Bulette
One would assume that fighting a shark on land would be an easy victory for Zoro but a Bulette is no ordinary shark. Their ability to tunnel within the soil and come up in the most unexpected of places would put Zoro on edge.
He would be unaware of where the next attack would be. His sword skills would be deadly if he could get off a quick hit or two but doing so against the fast-moving creature would be difficult, to say the least.
8 Destroy: Stone Giant
Stone Giants just look like powerful creatures that only a true hero could take down. Thankfully, for the most part, Stone Giants are peaceful unless provoked. Sadly, Zoro would be the kind of person to love to provoke such a massive creature.
He could take down a few since he could easily dodge their rock-throwing and land a few good hits on even the strongest Stone Giant. His skills with his sword would give him the edge in such a battle.
7 Good Fight: Gelatinous Cube
Who hasn't come across a Gelatinous Cube in D&D before? In fact, they are one of the most common monsters in the game.
Those swift on their feet can easily dodge them and keep their distance but those without a keen eye for their surroundings might find them to be deadly. Zoro is the type of person to face something head-on. He would try to attack from the front and possibly allow himself to be swallowed by the Gelatinous Cube.
6 Destroy: Displacer Beast
Zoro is at his best when he is able to rely on his sword and his skills as a warrior. This way of the warrior attitude allows him to contemplate various scenarios that he might face in any given battle.
As far as a Displacer Beast is concerned, its trickery would be of little use against someone as experienced as Zoro and its monster tentacles would soon be severed by his sword. Without its illusions and tentacles, the creature would be powerless against him.
5 Good Fight: Githyanki
Creatures and enemies that can match Zoro's speed are by far the hardest enemies he faces. His nature of trying to face such enemies in one-on-one combat might even the odds, especially when dealing with creatures such as the Githyanki who can read a person's mind.
This psychic ability would allow them to know his every move before he could even act on it, making it almost impossible for him to deliver a deadly, decisive blow. Chalk this one up as a coin toss as to who would win.
4 Destroy: Orc
Orcs are about as cut and dry of an enemy that Zoro could face. They, like him, are skilled with a blade and used to the weight that armor bears on them during any given fight.
Orcs also prefer to be face-to-face with their enemies in a fight, making it almost assured that Zoro could get in a few good licks before the battle even began to become serious. Orcs might be stronger than Zoro, but his speed would quickly even the odds, if not giving Zoro the overall edge.
3 Good Fight: Lich
Fighting the undead poses its problems for any person that is willing to take them on. For those without a magical affinity, these creatures are almost immortal as they can withstand any amount of carnage placed upon them by their enemies.
This would make a Lich one of the hardest creatures for someone like Zoro to take on simply because he is skilled with the ways of the sword and not with magical spells meant to take down any and all undead foes, leaving him at a disadvantage.
2 Destroy: Yuan-Ti
The Yuan-Ti are the perfect creatures that someone like Zoro would love to face in battle. Just like the Yuan-Ti, Zoro is trained in stealth and capable of listening to his surroundings, making the serpents' stealth advantage almost obsolete.
They would have no other choice but to fight him in hand-to-hand combat giving him the edge due to his experienced sword hand. Their inability to ambush him would put them on the defensive, allowing him to go on the attack for most of the battle.
1 Good Fight: Mind Flayer
Mind Flayers didn't become one of the more frightening creatures in the D&D world just because of their looks. They are conquerors by nature, enslaving native populations for their own nefarious needs.
Their overwhelming intelligence would pose a serious threat to someone like Zoro who would prefer just to hack and slash. Their ability to think on their feet and create multiple strategies with which to take him down would definitely keep him on his toes. Whether or not he could overcome such odds is unknown.
