Here is the full list of all 21 DeathMetal achievements.
Collected 100 bonuses total.
Collected bigger paddle bonus 10x.
Collected big balls bonus 10x.
Collected magnetic bonus 10x.
Unlocked Episode 2.
Collected fire bonus 10x.
Finished first level!
Collected smaller paddle malus 10x.
Collected tiny balls malus 10x.
Collected slow speed bonus 10x.
Collected high speed malus 10x.
Collected split ball bonus 10x.
Collected extra life bonus 10x.
Played with 4 balls at once.
Played with 6 balls at once.
Unlocked Episode 3.
Unlocked Episode 4.
Finished Level #10 in Episode 1.
Finished Level #10 in Episode 2.
Finished Level #10 in Episode 3.
Finished Level #10 in Episode 4.