The description for this is actually wrong. To unlock this achievement you will only need to reach Level 50 with Gennaro (The Conan looking guy who starts with the Knife) after unlocking the Randomazzo. The reason you need the Randomazzo first is because completing this requirement will unlock a new Arcane: "Iron Blue Will".
This Arcane will allow the following: weapons' projectiles to gain up to 3 bounces, the ability to pass through enemies and ignore walls: Knife, Thousand Edge, Axe, Death Spiral, Phiera Der Tuphello, Eight The Sparrow, and Carréllo.