Here is the full list of all 22 Alien Splatter Redux achievements.
Complete Stage 1 without dying
Score over 50000 points
Complete Stage 1
Complete Stage 2
Complete Stage 3
Complete Stage 4
Complete Stage 5
Complete Stage 6
Complete Stage 7
Complete Extra Stage
Complete Stage 2 without dying
Complete Stage 3 without dying
Complete Stage 4 without dying
Complete Stage 5 without dying
Complete Stage 6 without dying
Complete Stage 7 without dying
Complete Extra Stage without dying
Score over 100000 points
Score over 250000 points
Score over 500000 points
Complete the Boss Rush Mode
Complete the Glitch Worlds