To Hellfire and Back

Alliance: If you're a few short, Outland Sucks! is a fast and easy one, and a quest you very likely missed (as it's next to Thrallmar).

These are the quests (not including level 70 ones) that lead to the achievement.

Outland Intro Chain (4)

1. 
   
2. Through the Dark Portal
3. 
   
4. Arrival in Outland
5. 
   
6. Journey to Honor Hold
7. 
   
8. Force Commander Danath
9. 
   

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Expedition Point Chains (14)

1. 
   
2. The Legion Reborn
3. 
   
4. The Path of Anguish
5. 
   
6. Expedition Point
7. 
   
8. Disrupt Their Reinforcements
9. 
   

1. 
   
2. Know your Enemy
3. 
   
4. Fel Orc Scavengers
5. 
   
6. Ill Omens
7. 
   
8. Unlocks a lot of Honor Hold quests
9. 
   

1. 
   
2. Cursed Talismans and Zeth'Gor Must Burn!
3. 
   
4. Warlord of the Bleeding Hollow
5. 
   
6. Return to Honor Hold
7. 
   
8. Unlocks: Digging for Prayer Beads and Fel Spirits, see Honor Hold Quests below
9. 
   

1. 
   
2. Mission: The Murketh and Shaadraz Gateways
3. 
   
4. Shatter Point
5. 
   
6. Wing Commander Gryphongar
7. 
   

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Honor/Shatter Point Chains (5)

1. 
   
2. Mission: The Abyssal Shelf
3. 
   
4. Go to the Front
5. 
   
6. Disruption - Forge Camp: Mageddon
7. 
   
8. Enemy of my Enemy
9. 
   
10. Invasion Point: Annihilator
11. 
    

• 
  
• Make sure you pick up Burning Legion Missive for The Dark Missive
• 
  

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Honor Hold Quests (19)

1. 
   
3. 
   
4. Waste Not, Want Not
5. 
   
6. Laying Waste to the Unwanted
7. 
   

1. 
   
2. When This Mine's a-Rockin'
3. 
   
4. The Mastermind
5. 
   

1. 
   
2. Unyielding Souls and An Old Gift
3. 
   
4. Looking to the Leadership
5. 
   

1. 
   
2. Fel Spirits
3. 
   
4. The Exorcism of Colonel Jules
5. 
   
6. Trollbane is Looking for You
7. 
   
8. Drill the Drillmaster
9. 
   

1. 
   
2. The Dark Missive (Required drop: Burning Legion Missive)
3. 
   
4. The Heart of Darkness and Overlord
5. 
   

1. 
   
2. The Path of Glory
3. 
   
4. The Temple of Telhamat
5. 
   

• 
  
• A Job for an Intelligent Man
• 
  
• Hellfire Fortifications
• 
  
• Digging for Prayer Beads
• 
  

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Zeppelin Crash Chains (5)

1. 
   
2. In Case of Emergency...
3. 
   
4. Voidwalkers Gone Wild
5. 
   

1. 
   
2. Ravager Egg Roundup
3. 
   
4. Hellboar, the Other White Meat
5. 
   
6. Smooth as Butter
7. 
   

The Temple of Telhamat (12)

1. 
   
2. In Search of Sedai
3. 
   
4. Return to Obadei
5. 
   
6. Makuru's Vengeance
7. 
   
8. Atonement
9. 
   
10. Sha'naar Relics
11. 
    
12. The Seer's Relic
13. 
    

1. 
   
2. The Pools of Aggonar
3. 
   
4. Cleansing the Waters
5. 
   

• 
  
• Cruel Taskmasters
• 
  
• Deadly Predators and The Rock Flayer Matriarch
• 
  
• An Ambitious Plan
• 
  

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Longbeard Quests (5)

1. 
   
3. 
   
4. The Longbeards
5. 
   
6. The Arakkoa Threat
7. 
   

1. 
   
2. Gaining Mirren's Trust
3. 
   
4. The Finest Down
5. 
   

• 
  
• Rampaging Ravagers
• 
  

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Cenarion Post Quests (7)

1. 
   
3. 
   
4. Helping the Cenarion Post
5. 
   
6. Demonic Contamination
7. 
   
8. Testing the Antidote
9. 
   

1. 
   
2. Colossal Menace (They drop: Crimson Crystal Shard)
3. 
   
4. The Earthbinder
5. 
   
6. Natural Remedies
7. 
   

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Foreman Razelcraz Chain (4)

1. 
   
2. Outland Sucks!
3. 
   
4. How to Serve Goblins
5. 
   
6. Shizz Work
7. 
   
8. Beneath Thrallmar
9. 
   

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Ruins of Sha'naar (4)

1. 
   
2. Naladu
3. 
   
4. A Traitor Among Us
5. 
   
6. The Dreghood Elders
7. 
   
8. Arzeth's Demise
9. 
   

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Item Drop Quests (2)

• 
  
• Missing Missive
• 
  
• Avruu's Orb
•