i have a really weird theory:
1. have the entity starting with it's collision off and in a trigger zone.
2. the weapon is in a trigger zone that, when you go in it, you pick up the weapon at the same time as an invisible entity is associated with the player and follows the player.
3. use the 'entity within zone' condition so that when you step into the trigger zone near the entity;
I. the associated entity following you disappears
II. the entity in the trigger zone will turn its collision back on so that it can get damaged.
therefore the weapon will destroy it, but the fists won't at first because the collision is off, get it???
this is only a wild theory, and would probably tke a lot of trial and error to get working, but hey, it's an idea
so what's the job?