Here is the full list of all 15 Para Bellum achievements.
Complete the first level on normal difficulty.
Complete the first level on hard difficulty.
Complete the first level on very hard difficulty.
Complete the second level on normal difficulty.
Complete the second level on hard difficulty.
Complete the second level on very hard difficulty.
Complete the third level on normal difficulty.
Complete the third level on hard difficulty.
Complete the third level on very hard difficulty.
Complete the fourth level on normal difficulty.
Complete the fourth level on hard difficulty.
Complete the fourth level on very hard difficulty.
Complete the fifth level on normal difficulty.
Complete the fifth level on hard difficulty.
Complete the fifth level on very hard difficulty.