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