This guide was made by RadiantViper on trueachievements, so all credit to him/her for making this.
Spoiler warning! This list contains characters and quests which may be considered spoilers.
This is a list of all the side quests in the game. I have organized them by the quest giver, but I did this by memory so some of them may be a bit off. If you have any corrections, let me know.
Most side quests are marked by a yellow exclamation point on your map and mini-map, allowing you to easily find where to start the quest.
All quests must be done on a single difficulty mode - either Normal or True Vault Hunter. Completing half of them on one difficulty, then the other half on the other will not get you the achievement. As far as I know, you also have to do them on one character.
To my knowledge, none of the quests are missable. If quests are failed, they can be retried by going back to the quest giver. If quests are blocked, it means the quest giver is indisposed due to story reasons, simply continue (or complete) the story and you can finish them.
As far as I know, the "Creature Slaughter" missions are not needed for this achievement since they are pre-order DLC.
Finally, please note that you will have to advance the main story to get more of these quests. If the quest giver isn't giving you the quest, you just have to keep going until it's available.
Note for glitchy quests: Some quests in the game are known to glitch out for various reasons. Some of the glitchier quests include "Mighty Morphin", "Medical Mystery", and "Get To Know Jack". The only solution I can suggest is to do those quests from the start in someone else's game. If anyone knows any solutions for glitchy quests, please let me know.
- Note: Hammerlock later moves to Sanctuary
This Town Ain't Big Enough
Bad Hair Day
Handsome Jack Here!
- Pick up the ECHO just west of the exit out of Liar's Berg
Sanctuary Bounty Board
Assassinate the Assassins
The Good, The Bad, And The Mordecai
Clan War: Starting the War
- Leads to "Clan War: First Place"
- Note: Available after completing all "Animal Rescue" missions (and advancing the main story enough)
The Name Game
Rock, Paper, Genocide: Fire Weapons!
Rock, Paper, Genocide: Shock Weapons!
Rock, Paper, Genocide: Corrosive Weapons!
Rock, Paper, Genocide: Slag Weapons!
Safe and Sound
The Chosen One
Claptrap's Secret Stash
Claptrap's Birthday Bash!
Do No Harm
- Leads to "Medical Mystery: X-Com-municate"
Monster Mash (Part 1)
Monster Mash (Part 2)
Monster Mash (Part 3)
Cult Following: Eternal Flame
- Leads to "Cult Following: False Idols"
Mine, All Mine
- Leads to "The Pretty Good Train Robbery"
You. Will. Die. (Seriously)
- Note: You can only gain this mission after completing the final story mission. Please see the achievement for completing this mission for details on how to beat it
Borderlands 2 (Xbox 360)Secret Achievement
The Secret Achievement achievement in Borderlands 2 (Xbox 360) worth 49 points
Continue playing to unlock this secret achievement
Bearer of Bad News
This Just In
The Cold Shoulder
The Overlooked: Medicine Man
- Leads to "The Overlooked: Shields Up"
Rocko's Modern Strife
Capture the Flags
Hell Hath No Fury
Won't Get Fooled Again
- Started by talking to Marshall Friedman by Justin MacReady's corpse
- Started by examining the ECHO by the corpse outside of Moxxi's
- Started by talking to the group of 4 thugs in front of Scooter's garage
Three Horns - Divide
Happy Pig Bounty Board
- Note: "No Vacancy" must be completed to activate bounty board
Neither Rain nor Sleet nor Skags
The Ice Man Cometh
Medical Mystery: X-Com-municate
- Started by examing Doc Mercy's corpse after "Medical Mystery"
- Started by examining the ECHO on the wall at the Happy Pig Motel
Cult Following: False Idols
Cult Following: Lighting the Match
Cult Following: The Enkindling
Positive Self Image
Clan War: First Place
Clan War: Reach the Dead Drop
Clan War: End of the Rainbow
Clan War: Trailer Trashing
Clan War: Wakey Wakey
Clan War: Zafords vs. Hodunks
- Note: You actually get these quests from multiple sources, I believe some in the Dust and some in Highlands - Overlook. If anyone knows specific spots for these, let me know.
Too Close For Missiles
Out of Body Experience
- Started by examining the AI core from the Hyperion robot who destroy himself
You Are Cordially Invited: Party Prep
You Are Cordially Invited: RSVP
You Are Cordially Invited: Tea Party
The Pretty Good Train Robbery
No Hard Feelings
- Started by examining an ECHO dropped by a bandit after you kill him
Note for Self-Person
- Started by killing a Goliath in the main area, he drops an ECHO that starts this quest
- Note: Access this area by fast traveling to the fridge, the entrance is right across from the fast travel station
Bandit Slaughter: Round 1
Bandit Slaughter: Round 2
Bandit Slaughter: Round 3
Bandit Slaughter: Round 4
Bandit Slaughter: Round 5
Overlook Bounty Board
Stalker of Stalkers
The Overlooked: Shields Up
The Overlooked: This Is Only A Test
Hyperion Contract #873
Best Mother's Day Ever
- Started by finding the Mother's Day present, has a chance to drop from killing a stalker in The Highlands (both the main area and Outwash)
- Find the ECHO (marked by a yellow exclamation point on the map) to start this quest
Shoot This Guy in the Face
- Note: Also unlocks an achievement
Defend Slab Tower
Lynchwood Bounty Board
3:10 to Kaboom
Breaking the Bank
Animal Rescue: Medicine
Animal Rescue: Food
Animal Rescue: Shelter
Opportunity Bounty Board
Written By The Victor
- Start this by pressing the button near the "history" area of Opportunity, marked by a yellow exclamation point on your map
Jack Bounty Statue
To Grandmother's House We Go
- Note: Mal is located on the southern edge of the map, by the travel point for Ore Chasm
A Real Boy: Clothes Make the Man
A Real Boy: Face Time
A Real Boy: Human
- Note: You can access Ore Chasm from Eridium Blight, the travel point is on the south side of the map
Hyperion Slaughter: Round 1
Hyperion Slaughter: Round 2
Hyperion Slaughter: Round 3
Hyperion Slaughter: Round 4
Hyperion Slaughter: Round 5
The Great Escape
The Lost Treasure
- Started by picking up an ECHO inside a box (marked by a yellow exclamation point on your map)
Arid Nexus - Badlands
Fyrestone Bounty Board
Get To Know Jack
Hungry Like The Skag
- Kill skags in this area until one drops an ECHO recording that will start this quest