Here is the full list of all 19 Stewart The Fox achievements.
Finish the second level to get this achievement
Finish the first level to get this achievement
Finish level 1 in under 3.5 minutes!
Finish the third level to get this achievement
Finish the fourth level to get this achievement
Finish level 2 in under 3.5 minutes!
Finish level 3 in under 3.5 minutes!
Finish level 4 in under 3.5 minutes!
Kill the first Boss in level 3
Kill the second boss in level 4
Kill 25 Enemies.
Kill 50 Enemies.
Kill 75 Enemies.
Kill 100 Enemies.
Find all collectable Gifts.
Find all collectable TV's.
Find all collectable Orb's.
Find all collectables throughout the game!
Finish a level without dying.