Here is the full list of all 39 Outbreak achievements.
Purchased 20 pieces of equipment in Onslaught.
Cleared a wave in Onslaught.
Healed yourself 20 times.
Purchased a piece of equipment in Onslaught.
Cleared the Chasmal scenario.
Defeated 100 undead threats.
Constructed 50 barricades.
Cleared the Outbreak scenario.
Land 10 critical hits.
Cleared your first scenario!
Cleared the Tutorial scenario.
Constructed 10 barricades.
Defeated 20 undead threats.
Successfully overcame a puzzle.
You failed to survive.
Healed yourself.
Constructed your first barricade.
Defeated your first undead threat.
Defeated 1000 undead threats.
Healed yourself 200 times.
Cleared 10 scenarios.
Cleared 100 scenarios.
Solved 100 puzzles.
Survived 5 scenarios on Normal Difficulty.
Survived 3 scenarios on Hard Difficulty.
Survived a scenario on Biohazard Difficulty.
Survived a scenario on Hard or Biohazard Difficulty with one or fewer kills.
Cleared the Miasma scenario.
Cleared the Enkindle scenario.
Cleared all campaign scenarios.
Survived the first five waves in Onslaught.
Survived the first ten waves in Onslaught.
Survived the first fifteen waves in Onslaught.
Survived the first twenty waves in Onslaught.
Survived the first twenty five waves in Onslaught.
Survived the thirtieth wave in Onslaught.
Constructed 100 barricades.
Purchased 100 pieces of equipment in Onslaught.
Purchased 200 pieces of equipment in Onslaught.