Here’s the things I know that can definitely kill a shoggoth
katana or wakizashi
-needs niten or ninjutsu for maximum effect
martial arts; krav maga, scorpion, centipede, muay thai, tiger
-needs strength to be at least 30, so hydraulic muscles are a must. also need to be at full stamina. tiger claws, punch dagger, bionic claws or monomolecular blade handy as well. if scorpion style is being used, you need to corner it so it won’t be knocked back. if you lack hydraulic muscles, time dilation will suffice.
recoilless rifle
-one rocket should do.
heavy rail rifle
-about a full clip is enough
goo pit
lava or fire won’t kill them alone.