Here is the full list of all 27 Super Pig X achievements.
Ate 100 Bacon
Found 10 Dark Bacon
Beaten Level 4-X
Found Secret Exit
Beaten Level 3-X
Killed 100 pigs
Beaten Level 2-X
Ate 10 bacons
Found Dark Bacon
Beaten Level 1-X
Ate 1 bacon
Killed 10 pigs
Perfected a level
Killed 1 pig
Killed 1000 pigs
Found 50 Dark Bacon
Perfected 10 levels
Beaten Level X-X
Beaten Level Z-X
Beaten Level 0-X
Beaten The Game
Beaten All Levels
Enable Vegan Mode
Cheated
Enabled XP mode
Loaded Custom Level
Perfected all levels