Handsome Jack

Handsome Jack is the main antagonist in Borderlands 2. He has taken over the Hyperion corporation, declared himself dictator of Pandora, and stolen all of the credit for finding The Vault, going so far as to claim responsibility for killing The Destroyer. A new team of Vault Hunters is tasked with killing Jack and restoring (relative) peace to Pandora.

Jack has a geostationary moon base (in the shape of an 'H') in the Lagrange point between Pandora and Pandora's geostationary moon. It acts as an homage to his ego as well as a supply base from which he can send supplies and troops down to Pandora. The satellite also has a lens that allows Jack to keep an eye on the Vault Hunters at all times.

History
Little is known of Handsome Jack's life before becoming the CEO of Hyperion. Prior to his takeover, Handsome Jack worked as a programmer for Hyperion and was known simply as John, last name unknown. At least some of his early life was spent in the care of his grandmother, who was (at a minimum) physically abusive towards her grandson. The emotional trauma from these events was strong enough that as an adult Jack had his grandmother murdered, and no doubt contributed towards his mental decline.

Later in life John married and had a daughter, Angel, one of the universe's rare Sirens. Sometime after this his wife "disappeared"; though it is never explicitly stated, several ECHO recordings strongly imply that she died. The incident left further emotional scars; for example, the mere mention of his wife by a Hyperion employee led Jack to strangle the employee to death.

Shortly after his wife's disappearance, John placed the young Angel inside Control Core Angel in order to gain full access and control of Pandora's ECHOnet system, in the process irrevocably linking her to the facility. In an ECHO conversation with the Vault Hunters, Handsome Jack defends doing so, saying he had no choice after "what she did to her mother", though as with any statement from Jack it is unclear if this is a deliberate lie, delusional memory, or if Angel actually did something to her mother. However, a separate ECHO recording mentions the loss of a dozen Hyperion employees due to "accidents" relating to Angel, the incidents being compared to the disappearance of her mother.

With his daughter secretly in place, John began focusing most of his time and energy on gaining control of The Warrior hidden underneath Pandora's Vault, killing and manipulating his way to Hyperion presidency. During this time John began to use the name "Handsome Jack". Contrary to expectations, Jack's trademark mask did not come with his new name; ECHO recordings indicate that the mask was present even when he was known simply as John.

Jack used his daughter to gain full surveillance of Pandora and control of the ECHOnet system. Jack needed Eridium to keep her Siren powers at maximum yield, and it is implied that Jack's primary reason for the invasion of Pandora after the opening of the Vault was the abundance of this material appearing in the ground. He ordered the Hyperion military to forcefully take control of Pandora some time after the Claptrap Robolution.

Between the events of Borderlands and Borderlands 2, the Hyperion corporation dismantled all but one of the Claptrap units, annexed Fyrestone, and engaged in battle with the citizens of New Haven. Jack, with the help of Wilhelm, killed Helena Pierce and sacked the town of New Haven.

Handsome Jack sought to lure out Vault Hunters to his sphere of influence by displaying a need for them, then left them for dead in the Windshear Waste. He constantly communicates with them through the ECHOnet, taunting them, threatening them, and otherwise manipulating them. His building of Opportunity and the drilling into Pandora's core is no secret to the citizens of Sanctuary, but he still keeps a leaderly façade when addressing the citizens of Hyperion-settled villages.

Following Angel's death, he makes his first physical appearance and kills Roland. Lilith attempts to attack him, but is captured to replace his recently-deceased daughter as a catalyst to charge the Vault key. He rescinds the bounty on the Vault Hunters, vowing to exact vengeance himself for Angel's death.

His final appearance is at the Vault of the Warrior, and is fought as one of the two final bosses. After being defeated by the Vault Hunters, Jack takes the already-charged Vault Key and uses it to summon and control the Warrior. The Vault Hunters defeat it as well, thus ruining his plans for dominion over Pandora. Jack angrily chastises them for stopping him from bringing his vision of order to the lawless planet, and is then executed for his crimes.

After Jack dies, his mask falls off and his real face is visible. His face is deformed, with a vault symbol branded into it, and his left eye blinded. There are competing hypotheses about the cause of Jack's injuries: (1) Angel accidentally injured her father when she was young and unable to fully control her siren powers; (2) Jack was branded by a vault guardian or bandit before he turned the search for the vault over to the vault hunters; or (3) Jack was branded by his abusive grandmother when he was a child.

Quotes

 * Hey vault hunter, Handsome Jack here, president of Hyperion. let me just tell you how things work. Vault hunter shows up, Vault hunter looks for the new vault, Vault hunter gets killed. By me. You seeing the problem here? You're still alive. So if you could just do me a favor and off yourself that'd be great. Thanks pumpkin. (Heard during Blindsided, shortly before entering Knuckle Dragger's area.)
 * Hey! How - ah, these pretzels suck... So, how's your day been, buddy? We haven't really talked much since I left you for dead. Hey, you think you'll freeze to death out there? Nah, probably not. The bandits'll get you first. My day? It's been pretty good. Just bought a pony made of diamonds, because I'm rich. So, you know. That's cool. Kay, bye. (Heard during the Best Minion Ever mission on the way down to the first bandit camp after grabbing Claptrap.)
 * I’m rackin’ my brain trying to think of a name of that diamond pony I bought. I was gonna call it ‘piss-for-brains’ in honor of you, but that just feels immature. Maybe ‘Butt Stallion’? Nah, that’s worse. Tell you what, I’ll give it some thought. (Heard a little after the previous quote during the Best Minion Ever mission.)
 * This is Handsome Jack, thanking you, loyal test subject for helping bring Pandora into the future. The experiments you'll be put through will help us uncover new uses for Eridium, new cures for medicine and- Seriously? Why are you having me read this crap? This is freaking hilarious. They know we're gonna mutate the hell out of 'em, why lie to- (Wildlife Exploitation Reserve pre-recorded message.)
 * Ol' balloon tits is still holdin' a grudge against me, huh? I mean, don't get me wrong, I get it - once you've eaten prime rib for free, it's hard to go back to suckin' down hamburgers for cash. If you know what I'm talking about. Do you know what I'm talking about? (pause) Dicks. I'm talkin' about dicks. (During Hell Hath No Fury.)
 * Great! Say this to 'em: Don't be alarmed. I need you to stay calm and don't let on that anyone is talking to you. Start making your way off the bus. (ECHO log found during Get to Know Jack, repeated by Angel in the beginning of Borderlands.)
 * Screw you!  It would have been hilarious if it'd found it earlier.  Shut up! (After he finds his violin following Boss Battle at the Wildlife Exploitation Centre).

Trivia

 * He appears to have heterochromia, but his left (incorrectly colored) eye is actually a part of his mask.
 * His girlfriend was the Sheriff of Lynchwood.
 * He has a diamond pony called "Butt Stallion" (Jack clarifies to the Vault Hunters that it is in fact a living horse made of diamond).
 * Jack destroyed Mad Moxxi's Underdome after he thought she was cheating on him.
 * Jack's real face can be seen after defeating both him and The Warrior.
 * In the fifth ECHO recording during the mission "Get to Know Jack", Mr. Tassiter says "I know that beneath the ridiculous mask you are still a hideous, pathetic little nobody". This implies that Jack had his mask and scar before he completely took over the company and the events of the first Borderlands.
 * Handsome Jack was partially inspired by a particular interview with Nathan Fillion on Jimmy Kimmel Live.