You would think this achievement doesn't need another guide, however there is something worth pointing out here that isn't covered in any of the existing guides. You actually have to get torn apart by the zombies after dying for this achievement to unlock. Just dying may not be good enough.
I discovered this after letting myself die trying to get this achievement. No unlock. Figured 'oh great, this must be bugged for me or something', but I went for it again and on this occasion my character was actually ripped in two after death and then the achievement unlocked. Not sure how exactly to ensure this happens, whether it's related to how many zombies are around, which types etc, but this is what happened for me: I let two SWAT zombies kill me, no achievement, then I let one regular zombie beat me down and then I was torn apart by the subsequent zombies that spawned.
Also worth noting, you can easily copy your save to another storage device to avoid losing your characters when getting this achievement and