Here is the full list of all 14 Pencil vs. Eraser achievements.
Get hit by a snail.
Kill a snail with a mine.
Unlock everything
Death by poop... Gross
Erase 100 enemies.
Erase 1000 enemies.
Open the game 10 times.
Cover the page with 1000 eraser shavings.
Shoot 1 thousand bullets.
Destroy a spider web.
Allow an amoeba to replicate.
Get hit by a bouncy bullet.
Use a flower as a speedboost.
Fire 1 million bullets. Who has time for this?