o anyone who's played Through the Breach 2e... How do you actually take enemies out?

[Aldath]

I've been reading the game rules up and down all day, and all I see is that when they reach 0 wounds and every time you take damage after that, you make a roll to see if you pass out or keep fighting, and every wound thereafter is a Critical Hit, which has added effects.

But no where it says how to actually DEFEAT someone or kill it during battle, just AFTER battle in Narrative Time. Some enemies like Henchmen tier mobs and Undead automatically pass the tests to avoid passing out so... How do you ACTUALLY beat them?

By the look of it, battles can drag on forever if you don't get the right critical or manage to somehow apply bleeding out +10.

 

[Sernus]

There's a couple of ways, if you mean through damage:

(1) Critical Effects, for Fatemaster characters of Enforcer Rank and higer (and other Fated, too, should it ever come to that).  It may take a while, particularly if they're mostly taking Weak damage, but eventually the adds onto Critical flips for being way below zero Wounds get severe enough that every additional hit is doing a really nasty Severe Critical Effect. Eventually they either are so crippled they can no longer effectively fight, they Bleed Out and die, or the Critical Effect is high enough that it's an "insta-kill."

(2) Unconsciousness. Peon and Minion Rank Fatemaster character opponents generally fall unconscious as soon as they go to zero Wounds or below (with a few special exceptions). Enforcer-rank Fatemaster characters don't fall unconscious just for going to zero Wounds, but may still do so due to Spell/Manifested Power or Critical effects calling for an Unconsciousness Challenge that they then fail. Once unconscious, they're helpless. (Same is true for Fated characters.) 

Bear in mind that in many cases a reasonably intelligent and canny opponent who doesn't have a death-wish or isn't a raving lunatic will probably try to bug out and get away if they can, or try to surrender if they can't run, rather than just fighting until they die.  (Of course, there are always exceptions to this... maybe you're facing a real "death before dishonor" type like a Samurai bodyguard, or maybe a stitched-together monstrosity that doesn't worry about death because it's already been dead before... these, you just have to keep hitting until they stop moving!)

[EnternalVoid]

I will echo Sernus here, my group has chopped up their fair share of enemies so far *well mostly shot or bludgeoned*.

But a few things, first on page 302 under Unconsciousness, third paragraph from the bottom opens up with "Note that Undead or construct characters can fall unconscious as easily as living characters", so undead do not automatically pass it.  On page 313 there is an unconsciousness challenges section for describing how fatemaster characters react to it, which is basically the stuff Sernus was saying.

My group has found that they often have to get to negative 9-11 or so against Enforcers and the like to put them down as that is the point where even weak crits will flip their way up to the higher brackets and do lasting damage.  That said, once they are on negative wounds they have also found it 'easier' as many crits do things like slow, paralyze, negative to skills, or +2 to further crits.  Of course I often have enemies looking to run away, in a game not that long ago they were fighting Datsue-ba who decided after taking some injuries, being at negative 9 wds, and most of the Fated were still standing to just leave.  She had one arm busted, should have been bleeding out pretty bad *she does ignore bleeding out*, and some non-lasting injuries.

[Le gob]

We noticed that the fact minions are taken out at 0HP and bigger guys are not really makes a gap between them.

It's like the enforcers and henchmen have double HP, it makes them really hard to stop if they decide to flee. 

[Sunspotter]

Personally, while the core rules do tend to lean towards enemy survivability, I'm always one to keep to the tried and true "Chunky salsa" rule from Shadowrun. If a hit should by all means kill or at least incapacitate an enemy (or keeping with the original text of the rule "turn the target into something resembling chunky salsa") then it should drop like a sack of bricks. Even someone with henchman or master level abilities shouldn't be going after getting a cannon shot to the chest.