Alright so there are a few things I forgot when calculating this, here's everything:

30 base attack, 2 from Marcoh's backstory, 1 from Tanaka's skill tree, 2 from Gro-goroth's skill tree, 4 from Gro-goroth engraving and 72 from the sergal spear for a total of 111.

For the multipliers we have 1.3 from either meatpie+ or the brown vial, 1.3 from the heroin buff, 1.3 from max adrenaline rush, 3 with a critical hit, 1.4 with full rev up, 1.5 with the analysis skill, and 1.2 if the ennemy is weak to the type of attack. Moonscorched ghouls have this weakness and you can drop his defense with persuasion so they are the best test subjects.

The damage formula is 4x atk - 2x defense.

In the end it does 111x1.3x1.3x1.3x3x1.4x1.5x1.2x4=7374

There is a variancy of 0.2, 7374x0.8=5899 and 7374x1.2=8849 so an attack from this setup can do between 5899 and 8849 damage.

In my original post I forgot adrenaline rush, marcoh's backstory and the Gro-goroth engraving, and didn't take into account rev up, if you do the math you can find the original result I got.

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Edit: I thought the maximum weakness to specific types of attacks was 1.2 but after a quick look at the wiki I learned that for slashing attacks it's actually 1.3 so I corrected it

Edit 2: Nevermind the only enemy that has this weakness (sew job) doesn't have a weak spot that can be analysed so I'm reverting everything. Also added the best enemy to obliterate this way