Hmmm... it seems to in fact be performance based, although exactly how is a mystery. Of course, a high score is going to go with a great performance but a high score doesn't necessarily mean a great performance.
The obvious stuff: minimal damage, long combos, long Goregasms, headshots, get collectibles, save civilians. Avoid forced reloads? Maybe- the game obviously knows you didn't do a forced reload for the Never Runs Dry trophy so it's possible (although I don't know if manually reloading when you run out counts as a forced reload or just pulling the trigger again does) it could factor in. I sincerely doubt using Slow Mo-Fo Modes or Grenades penalizes you (although the latter gets you less points than if you headshot the enemies.) If they do, it ain't much because I used both when earning my "S" ranks on 7 of the levels.
Anyway, while I was waiting 10 minutes for the credits to roll, I though "Man, I hope I fucking got the "S" because this sucks balls. It'd be nice to know if I was on track." So on that note, here's my Overkill "S" stats: Story Mode with the regular alottment of zombies.
I got hit at least 4 times, probably 5 or even 6. One was a Puker which does 2blocks, if that makes a difference (and it was BULLSHIT because I shot that dude up while in Slow Mo-Fo Mode.) Another was a Mother stomp, which I think is another 2 blocks. I was using the Minigun (Hand Cannon on zombies attacking civilians), which is why my accuracy sucks compared to my earlier score posts. I also popped 4 Slow Mo-Fo Modes (I skipped the one by the civilian.) No Grenades though- you can't pick 'em up with a Minigun. So if you're doing about as well as I was, you are on track for an "S"... maybe.
And since Creeping Flesh was my last "S" rank (short stage means tight performance) here's those results...
combo of 67
Goregasm of 185.78
Hit once by those fucking Gregs.
ADD: I was just fucking around on another account and "S"ed Naked Terror with a pretty shitty run. Got hit several times and shot 2 civilians (BIG penalty) though I maintained combos and a Goregasm between mistakes. I'm inclined to think combos/Goregasms are the real deciding factors.
Last edited by stickghost; 01-12-2012 at 08:50 PM.