Here is the full list of all 12 Vex achievements.
The base game contains 11 achievements, and there is 1 DLC pack containing 1 achievements.
Complete the Pura Dimension
Complete the Ignis Dimension
Complete the Glacium Dimension
Complete the Quanta Dimension
Unlock the Iris Dimension
Unlock all 4 bonus levels
Kill 10 Patrol Enemies
Kill 25 Patrol enemies
Kill 50 Patrol enemies
Die from colliding with a Glide.
Obliterate 15 enemies using God mode
Complete the Iris Dimension