How does the "Bad Ending" work?

[Samz707]

I'm curious but sadly am currently unable to play Hammer & Sickle myself (due to the fact all the phyiscal copies have Starforce DRM which I don't want to risk and it sadly still has no digital version unlike S2 and Sentinels.) so I'm wondering how the "Bad Ending" works for when I do hopefully eventually get the chance to play it myself:

Is it just failing the plot that can cause it or is there a hidden counter of sorts that goes up when you get in combat with police and such? (So getting in avoidable gunfights slowly pushes you closer to the bad ending.) 

I'd like to play it myself to check since I'm curious but that may not be for a good while.