Nah, I'm good achievement

[Zod]

So for this achievement it says to kill Puff without a Tommy gun. And that's what I've been doing but for some reason I still can't get the achievement unlocked. Do i perhaps need to start from fresh?

[Square_Rabbit]

Are you using the Tommy Gun to kill the Bouncers guarding him? You need to kill Puff without even picking up the gun, so you need to dispatch the other zombies without it, too.

The achievement should unlock as soon as you kill Puff, rather than on level completion.

[John Helldiver]

Yah, you can't pick up the gun whatsoever, let alone use it on other enemies.