Topic post says it all really, I know of several. I just want to know if there is a Crispin-less ending really. It seems to me that there are several choices to make but that they don't necesarily count as alternative endings? Like, does having Clarity's head count as a different ending for those that it affects?

There are two Crispin-less endings -- one where you don't save Crispin but do save Clarity, and one where you save neither. (The Crispin-less endings result from not recovering his personality matrix and then either using the virus on Scraper or the plasma torch on the power core.)

As for how many there are, it depends how you count them.

(1) Return to the UNNIIC: (with Cr&Cl; with Cr only; with Cl only; with neither) x (Scraper killed with virus; Scraper not killed with virus)

(2) Jump from the tower

(3) Spread virus everywhere

(4) Blow up tower

(5) Join MetroMind

(6) Refuse to join MetroMind and die

I think that's it? Maybe I'm forgetting something. I'm not sure how to count the variants to the first one.

Ending 1: I told you to stop
Use Transmitter + Virus on Scrapper

Ending 2: Not bluffing
Use Plasma Torch on Power Core
No. You must be destroyed.

Ending 3: Too much power
Use Plasma Torch on Power Core
Very well.

Ending 4: Thanatos
Exit
Use Tracks
Use Transmitter + Virus on Radio

Ending 5: I always wanted to fly...
Exit
Use Tracks
Use Ledge
Jump

Ending 6: Resistance is futile
Talk to MetroMind
Very well, I will join you.

Ending 7: Live free or die
Talk to MetroMind
I will never join you.
Yes.

I've always thought of the variants of no. 1 all as separate endings:

1) Return to the UNNIIC with both Crispin and Clarity after having destroyed Scraper and found out about your origins as Horus

2) Return to the UNNIIC with both Crispin and Clarity without having destroyed Scraper or having found about your origins as Horus

3) Same as no. 1, though with only Crispin

4) Same as no. 2, though with only Crispin

5) Same as no. 1, though with only Clarity

6) Same as no. 2, though with only Clarity

7) Jump from the tower

8) Spread Thanatos virus by radio

9) Join MetroMind

10) Refuse to join MetroMind and get shot by Scraper

That's a whopping ten! :)

No, that's perfect (I think). I never experienced the Crispin-less ones, because I never made a save. Thirteen endings, impressive.

Scraper zapping for the win.

Yep, couldn't happen to a nicer 'bot! ;)