I recently tried going for my first diamond, the Strongman Diamond Badge, and I was under the impression that what weapon is attributed to kills was counted by whatever you had equipped in your primary weapon slot when a monster dies. So for my strategy, I went for Juggler and then had the Chainsaw/Azrael's Scythe in my prepared slot while keeping my primary slot empty, thus still allowing me to deal substantial damage with my "fists" and make the rest of the run past the Chained Court a lot easier. However while doing this and succeeding with a 100% killrate on HMP in a normal game, ensuring everything died while I had nothing equipped in my primary slot, I was not awarded the Strongman Diamond Badge.
So maybe I accidentally killed something when I used shotguns to weaken Demons in early levels or the couple of times I needed to blow a hole through a wall with a rocket, or maybe when I used Fire Skulls in the Mortuary it didn't count as fist kills, or maybe I accidentally left a weapon equipped in my primary slot when I melee'd something to death. However in the player records, it stated I have no fist kills on the Angel of Death, when I most certainly killed him with nothing in my primary slot, and I killed near a thousand Lost Souls in the run after Abyssal Plains got out of hand and an aborted attempt at getting the Iron Skull medal, yet the records listed only a few hundred fist kills on Souls. So are those records off, or does using Juggler to attack with a melee weapon in your prepared slot count as killing with that weapon instead of what is in your primary slot? And does using non-fist weapons at all prohibit you from getting fist-based badges/medals? Additionally, are item-based kills like from the Fire Skull attributed to your equipped weapon, or are attributed differently?
For one more piece of information, I did admittedly save scum to get the Scavenger Platinum from The Vaults during this run, where I did quit out and copied my save file back over until I succeeded in teleporting into the center vault. Would that have messed up the game's record keeping that resulted in my pre-Vault fist kills not counting?