The Prowler's front above multiplayer glory kill was given to the Imp because the works with the Imp model. I should also note that I added the lightning/energy effects, and that they're not part of the vanilla animation. But the animation is fully functional (and pretty cool), which is why I have included it. Either that, or some devs made it as a test or for a bit of fun. The telekinetic glory kill on the Imp was probably cut/unused because it does not fit the themes/mechanics/etc in the final game. If something looks off to you, this is why. This was worked around by placing a brief flash of light at Imp's chest to simulate the muzzle flash. I was able to work around this by attaching a shotgun to the Slayer's hands as a prop, but I cannot get the prop shotgun to actually fire like the real thing. The front chest shotgun glory kill for the Imp does not have an animation file for the shotgun. Ideally, if there were some kind of melee weapon that could be gripped similarly, I would use it instead of the shotgun, but I cannot find such an item at this time.
My best guess is that these animations were cut/unused because cutting someone in half with a blunt object seems unfitting, even if they are the Doomslayer. The fact that the shotgun fits in the Slayer's hands during these animations also backs up this theory. Following that logic, the shotgun is intended to be used in those animations. For reference, the other subwebs are killedByPlayer (regular glory kills), killedByPlayer_berserk, and killedByPlayer_chainsaw. In the game files, the shotgun melee kills for the Imp are listed under the killedByPlayer_shotgun subweb. Both Mancubi share the same files for glory kills, so a whole new set of glory kills would need to be defined if I were to keep the vanilla anims for the Cyber-Mancubus, which requires a lot of files to be edited, which conflicts with map mods.
The Cyber-Mancubus' MP animations replaced its vanilla animations because that was easier from a technical perspective. Some MP animations were not included as I couldn't get the body to ragdoll after death, resulting in them being frozen in strange poses after death I have tried to fix it, but I have no idea where the issue stems from. The Baron's rabbit punch glory kill is slightly misaligned.
This knowledge served as the foundation for the rest of this mod, and none of this would have been possible without their help! They helped me figure out the basics I needed to get the Revenant's multiplayer animations working in singleplayer.