Deidara

was the youngest member of Akatsuki and was partnered by Sasori and Tobi, consecutively, before his death.

Background
Deidara was originally from Iwagakure, although he readily abandoned the village for the opportunity of using his "art" more frequently as his village ridiculed him for it. Deidara became an assassin bomber for hire, not caring who he worked with so long as he could use his artwork. Sometime after Orochimaru left Akatsuki, Deidara was located by Itachi Uchiha, Kisame Hoshigaki, and Sasori, who were under the orders of the leader Pain to recruit him. Deidara refused at first, but was forced to join after being defeated by Itachi's Sharingan. Deidara, having taken a huge blow to his ego, carried a loathing for Itachi and other Uchiha for the rest of his life, though he was intelligent enough to recognize Itachi as a more powerful opponent.

Personality
Quick to anger and annoy, Deidara was a very hot-headed man. Something of a sadistic arsonist, he was not above relishing a good fight, and he often blew up his opponents in a very brutal fashion. Deidara's most distinctive trait, however, was his love of art. He would respect any form of it, even if it disagreed with his own. Deidara also had a habit of ending his sentences with nasal-like grunt, roughly translated as "yeah" or "hmmm". The latter is used in the VIZ version.

Deidara referred to his explosive ninjutsu as art, believing each bomb he made to be a significant accomplishment. He referred to his style as superflat (referring to certain types of art), and claimed pop (another art style) is dead. One of Deidara's catchphrases, "Art is a bang!" , was originally coined by famous Japanese abstract artist Tarō Okamoto (several of Deidara's explosives have resembled Okomoto's works too). Deidara was very proud of his art, to the point that he was simply unwilling to accept that anything could defeat it, leading to frequent overconfidence in battle.

Deidara referred to his partner Sasori as out of respect for him as a fellow artist. He also admitted, at least outwardly that Sasori was more powerful than he was. In spite of this, Deidara wasn't above goading his partner, and they frequently squabbled over the nature of true art (Deidara holding that art is transient and departing quickly; Sasori believing fine art is something wonderful that's left long into the future). This reflected their individual natures (Deidara made clay sculptures that explode; Sasori made long-lasting puppets out of humans). Deidara outwardly seemed to respect Sasori's beliefs, but couldn't resist getting a final jab in after Sasori's death.

Deidara's partnership with his second partner Tobi, however, was very different. Tobi apparently held a great respect for Deidara and frequently called him "senpai" (senior; VIZ, "partner"). Tobi's carefree and goofy personality did not please Deidara, who believed that all Akatsuki members should be serious and calm. Tobi frequently and unintentionally angered Deidara, which usually resulted in him attacking Tobi in a comedic fashion (e.g., blasting him with his exploding clay or strangling him with his legs). In battle, however, the two quickly set aside their differences and worked well together. Deidara also seemed to have a minor respect for Tobi, as shown when he apologized to his partner in his thoughts before he initiated his Self-Destruction.

Also, as revealed in the third databook; Deidara's favorite food was bakudan, a pun on the actual food (boiled eggs in surimi) and the Japanese word meaning bombs.

Rescue Gaara arc
Deidara, when partnered with Sasori, traveled to Sunagakure to capture Gaara and extract the Shukaku within him. Although he attempted a stealthy infiltration of the village, Deidara was quickly confronted by Gaara who launched an offensive against him. In the ensuing battle Deidara's left arm was crushed but he was still able to claim victory by mixing some of his clay into Gaara's sand, causing Gaara's own weapon to backfire. With Gaara captured, Deidara and Sasori convened with the rest of Akatsuki to extract Shukaku.

When Team 7 arrived at their location, Deidara took Gaara's body to lead away Kakashi and Naruto (the container of the Nine-Tailed Demon Fox), leaving Sasori to deal with Sakura and Chiyo. Kakashi used his Kamui to sever Deidara's other arm during the pursuit, giving Naruto a chance to retrieve Gaara. Handicapped and outnumbered, Deidara used a Suicide Bombing Clone to escape. Knowing Sasori to have died during his battle, Deidara goes looking for his arm in order to get back his Akatsuki ring. He finds it in the possession of Zetsu and Tobi.

Three-Tails Arrival arc
Deidara appears later with his arms successfully reattached by Kakuzu. In the anime, he and his new partner Tobi find that their next mission is to capture the Three-Tailed Beast. Along the way, Tobi insists that he is exhausted (to which Deidara contradicts) and suggests that they should take a break at a nearby dango shop, to which Deidara apparently agrees. Deidara also shows an interest in what Tobi looks like behind his mask, only for him to be tricked by Tobi to look away for a moment. However even when they stop for a bite to eat, Deidara is ultimately angered by Tobi to the point of blasting Tobi across the forest with one of his bombs in response to calling his art a "rip-off".

Hunt for the Uchiha arc
Deidara is later seen with Tobi assisting him in capturing the Three-tailed Demon Turtle. He then tows it to a location where it can be sealed, but gets into a dispute with Tobi over who actually captured it. They are subsequently seen extracting the Two-Tailed Demon Cat before sealing the three-tails as well. During this time he had new arms sewn onto his body by Kakuzu.

After sealing the Four-Tailed Beast, Deidara hears about the death of former Akatsuki member Orochimaru. Having wanted to kill Orochimaru himself, Deidara and Tobi seek out Orochimaru's killer: Sasuke Uchiha. When they finally find Sasuke, Tobi assists in Deidara's assault against him. When Sasuke proves able to counteract all Deidara's efforts because of his Sharingan and lightning-based abilities, Deidara makes one last attempt to defeat the Uchiha by blowing himself up. The attempt failed, as Sasuke summoned Manda to protect himself at the cost of Manda's life, leaving Deidara's death to be in vain.

Intelligence
In addition to his clay-based abilities, Deidara was very intelligent, often using tricks, misdirection, and calculated gambles to get his explosives in range of an opponent. As a long-range specialist, he was weaker in close combat, but skilled enough to hold off a close combat specialists like Team Guy, handling a kunai in his mouth, and had a variety of techniques in his arsenal to escape close quarters when necessary. Deidara's abilities were well recognized within Akatsuki and the leader, Pain, openly admitted that he was something unique, and that his loss was a major blow to the group.

Exploding Clay
A fancy and skillful fighter, Deidara possessed special mouths in the palm of each hand to create Exploding Clay, chakra infused clay that detonates with the command and a single-hand hand seal. This clay could be molded into a wide variety of shapes and forms, growing to large sizes when infused with chakra (with Deidara performing the necessary hand seals) and could be controlled at will. This allowed him to create living explosives to attack opponents at long range. Deidara could even create clones from the clay, named Suicide Bombing Clones, that could be a deadly surprise for opponents. Deidara's clay creations ranged from microscopic to gigantic in size, allowing him to adapt to any situation. Deidara could also use the clay for other purposes, as he was frequently seen creating birds to be used for transportation. It seemed he also knew standard earth-based jutsu as shown from his Earth Release: Mole Hiding Technique, which he used to avoid damage from one of his mass-scale bombs. However, he could potentially run out of clay if he used too much of it, leaving him vulnerable.

Eye Enhancement
He also wore a scope on his left eye for long-range observation, and he had trained the eye itself to counter genjutsu, allowing him to see through and negate them. This was done in response to Itachi's powerful genjutsu skills, of which he had a considerable loathing and resolved to defeat if he got the chance.

Trivia

 * Deidara ranked 3rd in the most recent official character popularity poll, one rank above Naruto. He also ranked higher that any other member of Akatsuki (though at the point that poll was taken, only about half of Akatsuki's members were formally introduced).
 * According to Pain, Deidara's reason for fighting is "Just Because".
 * Unknown to him, his partner before his death, Tobi, has the kekkei genkai he despised the most: the Sharingan.
 * Deidara was apparently very curious as to what was behind Tobi's mask, as when they stop to eat dango during the Three-Tails arc, he begins to tense up when Tobi begins to remove his mask to eat.

Quotes

 * (Catchphrase) "Art is a blast!"
 * "Fine art is the beauty of that single fleeting moment of explosion."
 * "Life's only beautiful… because it's so fleeting, so transient."
 * (After discovering Sasori's death) "''Like anything is left for the future as a thing of eternal beauty... He got killed straight off!'
 * (Last words to Sasuke) "Now show me your fear! Drown yourself in the awe... and despair! Cry like a lost child! Because my art... is a BLAST!"
 * (To Sasuke) "Those eyes!! Those goddamned cocky eyes of yours! It drives me insane!"