Zer0 is the playable Assassin class character in Borderlands 2.
He was revealed on February 21, 2012, in the Borderlands 2 Launch Date Trailer. His origins and real name are as of yet unknown. He works as an assassin, as much for the challenge as for the money; he even tells targets to fight back and give him a challenge. He is simply called "Zer0" because when he dispatches an enemy it displays a "0" on his faceplate. Other emotes, such as a "smiley face," pop up on his faceplate during different actions.
Zer0 is an assassin for hire, wanted for political killings as stated by his wanted poster. He appears to also work more common hits. In his ECHO recording that he starts out with in the game, he is about to kill one of his targets. The target apparently murdered a man, and claimed Zer0 must have been sent by the victim's sister or children, and offers to pay Zer0 quintuple what they're paying. In a haiku, Zer0 remarks on how he wants the "Poor Shmuck" to fight back and proceeds to say he wants a challenge.
Action Skill: Decepti0n
Decepti0n grants Zer0 the ability to deploy a holographic decoy of himself and enter an invisible "stealth mode." While cloaked, he can maneuver about the battlefield dealing amplified damage on his next attack. The longer Zer0 stays cloaked the more damage he can inflict to enemies; however, the shorter Zer0 stays cloaked, the sooner he is able to use the skill again. Zer0 does not enter a separate dimension like Lilith when she Phasewalks, and can still take damage from grenades and other forms of splash damage while cloaked.
Decepti0n has a base cooldown of 15 seconds and gives up to +650% Melee Damage or +200% Gun Damage and +250% Gun Critical Hit Damage.
This tree focuses on guns, particularly sniper rifles.
|Headsh0t||1||5||+5% Critical Hit Damage per level.|
|0ptics||1||5||+3% Zoom and +12% Aim Steadiness (reduces aim disruption when taking damage) per level.|
|Killer||2||5||Kill Skill. Killing an enemy gives you +10% Critical Hit Damage and +15% Reload Speed per level for a few seconds.|
|Precisi0n||2||5||+5% Accuracy per level.|
|0ne Sh0t 0ne Kill||3||5||The first shot from a fully loaded magazine deals +12% Damage per level.|
|Vel0city||3||5||+20% Bullet Speed, +3% Critical Hit Damage, and +2% Gun Damage per level.|
|B0re||3||1||Shots pierce through enemies, gaining +100% damage per enemy pierced. Enemy crit locations highlighted in Decepti0n.|
|Kill C0nfirmed||4||5||Up to +8% Critical Hit Damage per level depending on how long you aim down the sights.|
|At 0ne with the Gun||5||5||+25% Hip-Shot accuracy, +10% Reload Speed, and +1 Magazine Size with Sniper Rifles per level.|
|Critical Ascensi0n||6||1||Scoring a Critical Hit with a sniper rifle gives you +6% Critical Hit Damage and +5% Damage with sniper rifles. Can stack up to 999 times. Stacks begin to decay if you haven't scored a critical hit in a while.|
This tree focuses on improving Decepti0n, and abilities that benefit both ranged and melee combat.
|Fast Hands||1||5||+5% Reload Speed and +10% Weapon Swap Speed per level.|
|C0unter Strike||1||5||After getting hit, your next melee attack has a chance to deal +50% damage per level.|
|Fearless||2||5||+5% Fire Rate and +3% Gun Damage per level when your shield is depleted.|
|Ambush||2||5||+4% damage per level when attacking enemies from behind or when attacking an enemy who is targeting someone other than you.|
|Rising Sh0t||3||5||Each successful ranged or melee attack gives you +2% Gun Damage and +1.8% Melee Damage per level for a short time. This bonus can stack up to 5 times. Faster weapons can gain stacks more quickly, but slower weapons retain stacks for a longer period of time.|
|Unf0rseen||3||5||Your holographic decoy explodes when you become visible again, causing shock damage to nearby enemies. Damage increases per level.|
|Deathmark||3||1||Dealing melee damage marks a target for 8 seconds. Marked targets take 20% additional damage from all sources.|
|Innervate||4||5||While Decepti0n is active you gain +2% Gun Damage, +7% Movement Speed, and regenerate 0.8% of your Maximum Health per second per level.|
|Tw0 Fang||5||5||Every time you fire you have a 6% chance per level to fire twice.|
|Death Bl0ss0m||6||1||Action Skill Augment. Throws a handful of Kunai knives. Has a random elemental effect. Does not take character out of Decepti0n. Can be used five times per cooldown. Can apply Death Mark.|
This tree focuses on melee attacks.
|Killing Bl0w||1||5||+100% Melee Damage per level against enemies with low health.|
|Ir0n Hand||1||5||+3% Melee Damage and Maximum Health per level.|
|Grim||2||5||Kill Skill. Killing an enemy regenerates 0.7% of your shield per second and gives +1.5% Action Skill cooldown rate per level for a few seconds.|
|Be Like Water||2||5||Shooting an enemy gives +6% damage per level to your next melee attack. Melee Attacks give +4% damage per level to your next gun attack.|
|F0ll0wthr0ugh||3||5||Kill Skill. Killing an enemy gives +8% Movement Speed, +6% Gun Damage, and +8% Melee Damage per level for a few seconds.|
|Backstab||3||5||Your melee attacks deal +8% damage per level when hitting an enemy in the back.|
|Execute||3||1||Melee Override Skill. While Decepti0n is active and a target is under your crosshairs, melee to dash forward a short distance and perform a special melee attack, dealing massive damage. Has a range of 3 meters.|
|Resurgence||4||5||Killing an enemy with a melee attack restores up to 4% of your health per level depending on how low your health is.|
|Like The Wind||5||5||+3% Gun and Melee Damage per level when moving.|
|Many Must Fall||6||1||Killing an enemy with a Melee Attack during Decepti0n deploys an additional holographic decoy and extends the duration of Decepti0n instead of ending it.|
Zer0's basic melee attack uses his sword. The sword is not an equippable item but its effectiveness in combat can be enhanced. The sword's hilt "exists" but the blade digistructs when the hilt is pulled from its sheathe.
- I am bored. / I would like to kill things. / Can we go?
- What's the hold up? / Is someone in the bathroom? / Are you on the phone?
- What is going on? / Why have my limbs stopped moving? / Has my heart stopped?
- Bored!(repeated numerous times) / I am really BORED!!
- Boredom is my taunt, / As I lack autonomy / To move my own feet.
- An idle mind is / A very dangerous thing. / I think of violence.
- I am bored as hell / I would like to kill something / Can we friggin go?
- Your eyes deceive you; / An illusion fools you all. / I move for the kill.
- How hilarious. / You just set off my trap card -- / Your death approaches.
- The true world revealed -- / Weakness is now known to me. / Time to go to work.
- And I disappear; / A ghost amidst the combat, / Preparing to strike.
Scoring a critical hit
- A critical hit; / So very satisfying. / I live for such kills.
- Critical killing / Is an art unto itself; / And I am Rembrandt.
- A critical kill / Showers me in blood and spit / How enjoyable
- I enjoy that.
- Hee hee.
Affected by an elemental attack
- I feel the burning / Eating through my equipment! / Must stop, drop, and roll.
- I'm covered in slag! / I must seek cover quickly, / or pain is coming.
- Disgusting, this slag / Inelegant chemical / Increases damage
- A new instrument, / Waiting for a sonata / That I will conduct.
- I want that.
Comparing items in the menu
- Comparisons made, / But which is superior? / A tough decision.
Reviving a downed ally
- I have you.
- Keep shooting!
Killing an enemy
- A most confused death / Dead before he even knew / Where I had struck from
- Striking from nowhere / Killing with accuracy / This is who I am
- I am everywhere / And yet I am nowhere too / I am infinite
- I am nearly dead / It's time for a second wind / Let my aim be true
- I will not die here / I still have too much to do / And so much ammo
Getting a Second Wind
- I won't die today / Not while I still have ammo / I am a badass
- I have arisen / You will regret harming me / My Vengeance at hand
Zer0 often displays holographs from his faceplate, revealing his emotions through this. Known ones include:
- :) - an emoticon smiley face, displayed randomly
- 0 - a large zero, displayed when an enemy is killed with a melee attack
- :D - an emoticon smiley face, displayed when constructing and/or entering a vehicle at the Catch-A-Ride
- WTF BRO - an acronym for "what the fuck, bro", displayed when crashing into something in a vehicle
- <3 - an emoticon heart, displayed while reviving a friendly player
- FML - an acronym standing for "fuck my life", displayed while downed
- ? - a question mark, displayed when pending actions (such as switching seats with a player in a vehicle)
- ! - an exclamation mark, displayed when seeing a downed friendly player
- $ - a dollar sign, displayed when completing a mission
- && - twin ampersands, displayed when inspecting items in the menu
- 勝 - A kanji character meaning "victory", displayed when receiving items by either picking them up or via trading
- ... - ellipsis, displayed when either inspecting menu items, after killing an enemy, or while reloading a weapon
- Gearbox concept designer, Scott Kester, credits Zer0's inspiration to "loner characters" like Snake Eyes from G.I. Joe and Gray Fox from the Metal Gear video game series. 
- Zer0's Class Mod is represented by an attachment on his elbow.
- The bounty on Zer0's head is $32,000,000,000.00
- One of Zer0's dialogue lines when using Decepti0n, "How hilarious, you've just set off my trap card," is a reference to the anime Yu-Gi-Oh where characters would often say the same thing when revealing a trap card. The term is also used as an internet meme, usually said after a successful deception of someone else.
- Most of Zer0's dialogue is spoken as a haiku, something that is noticed by Handsome Jack in an ECHO recording.
- One of Zer0's heads, known as "Alienati0n" is a reference to the Alien franchise.
- One of Zer0's skins, called "Why so Serious?"(a black and green color swap of his default costume) is a reference to an iconic line in the movie The Dark Knight.
- One of Zer0's skins, called "Mutant" (a green and yellow color swap of his default costume) is a reference to the popular Teenage Mutant Ninja Turtles series. The blue highlight on some of his faceplates is a reference to Leonardo, the de-facto leader of the turtles who is also known for his katana.
- In the doomsday trailer, Zer0 says "September 18, 2012," The release date of Borderlands 2. He also says it again, later in the video.
- Another of Zer0's skins, Toad of Battle, shares the color scheme of the main characters of the game Battletoads.
- Zer0 has four fingers per hand (three plus thumb) as opposed to the human five. This may indicate that he is, indeed, inhuman as many speculate. Or maybe he has 2 fingers in 1 glove part.