1 - What's their attitude?
Any/all of the above. What makes a good zako isn't alignment. They could even be "redshirts" or "green helmets" for the Good Guys (tm). The point is that they're in a large group taking on a single hero or small squad of protagonists. And here by "hero" I mean "named character of exceptional skill/ability" not necessarily a Good Guy like you would want to take home to your parents.
2 - What's their uniform?
I am much less flexible here. Full coverage or realistic/practical combat gear, while almost always cool, is almost never hot. I need my zakos to be nude, lewd, or at the very least in skimpy/slutty fetish gear. Now within those parameters, it can be pretty much anything, but there are still a few themes I find mostly uninteresting (French maids, nuns, and school girls mainly).
3 - What weapons do they use?
This depends on the setting. I should mention I like a wide variety of settings, ranging from sword & sorcery-type stuff to post-apoc to far-future intergalactic space crap. That said, I like it when everyone's "playing for keeps". They can be unarmed like if they're a martial artist or some kind of CQC monster, but they're going to do FATALITIES.
4 - How skilled are they?
This one doesn't matter so much. Or, at least, I like a little variety here. Cowardly bullies who never stood a chance, anxious greenhorns in over their head, competent but still-outclassed by the hero(es), mini-boss types who can hold their own for an episode... I like 'em all. But I feel like named, recurring antagonists fail to be zakos by definition.
5 - Do they survive?
Here again, and while I know this one can be contentious, non-lethal takedowns don't really do it for me. The zakos don't need to be wiped out, necessarily. The heroes can spare some, take prisoners, or allow enemies who flee to escape, but I'm not really here for G-rated brawls, superpowered or otherwise. And I actually DO like it when the zakos are wiped, or killed while trying to escape/surrender. What I DON'T like is torture or extreme gore. The protagonists either don't take prisoners, or they treat them humanely.
6 - What's their age range?
I'm not particular about their ages. The important thing is that the majority of zakos are relatively inexperienced, and that this comes out as either bravado or skittishness in the face of the protagonists.
7 - Do you care about their background?
I need them to be real people. I'm not interested in zombies, robots, or brainwashed abductees. They can still be clones or whatever, but they need to have their own emotions, minds, and lives.
8 - Describe your perfect zako scenario?
I don't really have a "perfect" zako scenario. I'm sort of quantity over quality here. The best thing for me is a setting with lots of crime or a big stupid war that can support a lot of different armed groups and some real big armies/organizations. I like everything from big, set-piece battles with massive casualties to ninjatastic "infiltrate the base" scenarios. And everything in between.
Now for the attacker:
1 - What's their attitude?
Sad samurai, cold mercenary, damaged sadist, I like them all. They can be ruthless, and they can enjoy it, but I just can't deal with torture. Leaving a wounded enemy for dead is one thing (I like drawn-out death scenes in general), but I tune out the second the hero starts torturing captive enemies or raping them. Sex is fine, and I really like it when the hero comforts or sends off a dying enemy with one last handjob or w/e, but I don't really like it forced or coerced.
Overall, there's probably nothing I dislike more than "Big Buff Manly Man Dominates and Humiliates Uppity Inferior Lady-Types". The Hero(ine) can be cold, sadistic, sentimental, romantic, whatever. They just can't be motivated by a hatred of women in general. They can be motivated by revenge or hatred of this specific zako group, but misogyny is a serious turn-off.
2 - What's their gender?
Don't care, as long as they're attractive and feminine. Same thing goes for the zako, too. They can be male, female, both, or neither. Just as long as they have cute faces and feminine hair and skimpy/slutty outfits.
3 - What type of equipment do they use?
While quick and clean kills don't bother me, I lose interest when it's ALL headshots and neck-snaps. On the other hand, bodies being burned, blown apart, or crushed can be altogether too much for me. Blunt weapons, large-caliber guns and flamethrowers tend to produce more guro content than I'm really ever up for. I think I like small-caliber guns and sharp/edged weapons because the zako can bleed out and roll around for a while. The things they say and noises they make while they die are a huge part of what I find interesting.
4 - What is their fighting style?
See above. Melee or ranged, I tend to prefer fast heroes with lots of finesse.
