Due to his actions, he can be considered the tertiary antagonist of Impel Down Arc, and one of the main antagonists of the Marineford Arc, the Summit War Saga, and the remainder of the series overall.
During his raid on Banaro Island, he had added a large black and gold captain's coat over his attire, along with white beads on each wrist as bracelets and rings with gemstones on all of the fingers of both his hands (similar to his predecessor, Crocodile).
At the Shichibukai meeting at the Marine Headquarters, he added a pair of necklaces of red as well as golden-yellow and blue beads to his dark orange sash and a traditional black tricorne hat over his grey bandana, as well as switching to a red shirt, while wearing his captain's coat like a cape. He also has three flintlocks and a flask tied to his sash around his waist.
In the Volume 63 SBS Oda drew the Shichibukai as children. Teach is shown wearing a baseball cap with a rolled up long sleeve shirt and green shorts. He is also wearing black curled tip shoes, and unlike his usual cheerful expression, is crying for an unknown reason.
After the time skip, Teach has grown a long beard that he has split into multiple sections, very much like his real life basis. He also wears a new hat with his Jolly Roger embroidered on it.
Many of One Piece's characters are given a distinct laugh. Blackbeard follows this tradition by starting his laughs with "Ze" (i.e. Zehahahahahaha!). This laugh is not present in the English Dub until the Banaro Incident. Blackbeard's personality seems to be a strange mix of courage and cowardice, high intellectual capacity and stupidity. While at times his character looks strong and fearsome, in others he will seem weak and ridiculous. He is apparently very deceptive, joining the Shichibukai in an elaborate and convoluted fashion for the sole reason of gaining access to Impel Down in order to find new crew mates and later resigning from it in front of the fleet admiral himself saying that he does not need it anymore. He is also exceedingly power-hungry and greedy, aiming to become the next Pirate King. His hunger for power lead him to fashion a very cruel way of recruiting only the best prisoners in Impel Down as comrades: he ordered them to murder each other, and would only take the strongest ones who survive. Though he betrayed the Whitebeard Pirates, Teach takes comradeship with the crew he formed to a high level, made evident when he was willing to make a trade with the Marines for a battleship big enough to hold all of them comfortably for the sake of one crew member, Sanjuan Wolf. Despite his obvious malevolent nature, he is also genuinely compassionate, caring, sympathetic and empathetic towards his crew's well-being and is willing to take assaults intended for his crew. He also has an extreme thirst for adventure, regularly traveling from place to place. However, he tends to play it by ear.
Blackbeard, like others who carry the Will of the D., has a strong belief in fate and the dreams of men, but unlike the others, is the only one who truly seems to take it to heart. He shares several attributes with Luffy, including having a voracious appetite, carefree attitude, competitive and reckless nature, persevering even if there may be grave consequences, and huge ambitions to follow his dream of finding One Piece and become the new Pirate King. Despite that, there is also a great contrast between him and Luffy: primarily, Blackbeard fears death whereas other D. carriers embrace it if it comes, and was willing to betray his own friends for power. Just before his death, Whitebeard noted that Teach was not the one Roger had been waiting for and dismissed Teach as being incapable of continuing Roger's legacy.
Perhaps because of his strong belief in fate, Blackbeard is highly amoral. He believes that there is no inherent "good" nor "evil" in the world, jeeringly mocking anyone who expresses such belief. He is also patient and conniving, having spent decades on Whitebeard's ship just to get his hands on the Devil Fruit he wanted, before killing Thatch and leaving the crew. His nihilistic tendencies are in line with the power of the Yami Yami no Mi he possesses, which is said to reduce everything to "nothingness". During his raid on Impel Down, he stated that his plans have not gone exactly as expected, but is willing to take these surprises in stride. He handed Portgas D. Ace to the World Government and finally killed his captain Whitebeard. Despite this, he still displayed respect for his superiors during the events, referring to Ace as his commander, and said that he aspired to be like Whitebeard. He showed his ruthlessness when he killed Thatch, and with his crew's help finished off his former captain, Whitebeard.
Blackbeard is often very calm, composed, relaxed, easygoing, cheerful, and free-spirited, but he can be surprised and startled, such as when Coby told everybody present to stop the war, or when Whitebeard had held him by the throat. He is very politely sarcastic and mocking towards those around him, such as when he taunted Luffy, about Ace's inevitable execution, or when he mocked Whitebeard for his age.
He is also overconfident, and while very powerful, tends to converse and/or taunt his opponents in the middle of battle. He has done this in every battle he has been shown in, and as a result, he always suffers a heavy, painful attack while his guard is down. Such as when he taunted Whitebeard about not being able to use his powers, and nearly got cleaved in half with Whitebeard's bisento or when he boasted in front of Magellan and was nearly drowned by the Hydra attack, only surviving because Shiliew gave him and his crew the antidote. His overconfidence also made him believe that he could do a trade with the Marines despite having betrayed them already, which once again proved a mistake. Since having acquired two Devil Fruit powers, he has developed a severe superiority complex, believing himself to be truly invincible and the strongest of them all, while revealing his goal of world domination. Despite his arrogance, Blackbeard does show a sense of caution, as he refused to fight Shanks and his crew, as well as Admiral Akainu when he was aboard the Marine battleship that they wanted.
Blackbeard is a very patient and careful pirate, as stated by Shanks. Unlike other powerful pirates, he never gained renown and remained concealed, and only makes his moves when he sees an opportunity for power.