The Fist of Zeromus, or the Black pikmin army are, needless to say, a violent bunch. This isn't to say though, they aren't organized.
The main bulk of the Black Pikmin army, led by Kazul. These are troops who use their unique skills to fight; most of them do not wear armor, instead preferring to get into the brawl and rely on their own power to win. Their skills can vary wildly.
The heavy weapons guys, led by Blackfuse. They handle the artillery and almost anything mechanical; their powers often allow them an increased efficiency with their machines. Most of these devices would not last under scrutiny; they're not so much held together by tape and chewing gum as hopes and prayers. Almost literally; a Black Pikmin Mek will only work for a Black Pikmin, so long as he thinks it should work. Most of them are very difficult to convince otherwise.
Black Pikmin with powers suited to defend, led by Barricade. Anyone with a power that can defend or heal is placed in this group, from shields to simply being impervious to damage.
Black Pikmin with powers not suited to direct combat, or falling under any other field, are placed in this Skwad and outfitted with heavy powered armor. Led by Trombe, and occasionally mocked by the other Skwads as "Compensators" for wearing armor, they nevertheless prove themselves to be impressive fighters, and can be extremely dangerous when cornered.
Led by Epsilon and thus lacking the Orkish accent, this group is comprised of those with powers suited for stealth. Like the sniper himself, these guys snoop about and covertly remove potentially dangerous targets on the battlefield. This covers a pretty wide variety of espionage tactics, from simply being invisible to infiltrating enemy squads. Careful with these guys...
Exceptionally intelligent Black Pikmin with psychic powers. Led by Barrack, they provide innovations to Black Pikmin tech and reinforce their comrades with their power. The source of their power is dangerous, though, and backlash for drawing too much power can be... explosive.
Pikmin of any color, though mostly Black, that have fallen and been re-raised into Undeath by Arkthugal or one of the Prime Disciples. Composed of one Blood disciple, one Frost disciple, and one Unholy disciple, any one team is a major force to be reckoned with. Should one fall, the Unholy disciple can revive them, though should the Unholy disciple fall, both of the other two must work to revive him. All Death Knight teams are bound to their two brothers; they cannot venture far from one another, or they will die.
Even Black Pikmin who lack wings or some other form of natural flight like to fly, so the only recourse in this case is to strap ad-hoc jetpacks to their backs. And by jetpacks I mostly mean repurposed missiles. Led by Skyshatter, these boyz like to jump on their targets from high places and flatten them in one go. And then do it again.
Led by Kanaedolph. See Rakuen Maigo for more information.
Black Pikmin who lived a thousand years ago, their congealed blob of Black Nectar was trapped in Demetri's alternate dimension, where it encountered a shade. From this shade, they learned to manifest themselves as phantoms and once more fight for the Black Pikmin. Led by Black Art, their incorporeal forms are nearly indestructible, making them a terrifying force to behold.
Axe Crazy, Authority Equals Asskicking/Asskicking Equals Authority (both in equal measure), Blood Knight, Clap Your Hands If You Believe (Their mechanical devices literally run on this), Funetik Aksent, For the Lulz, For the Evulz, Monogender Monsters (No female Black Pikmin), Moar Dakka, Roar Dakka (These guys like making noise), Large and In Charge (Stronger Black Pikmin tend to grow huge), Improvised Weapon, Elite Mooks (ALL OF THEM), Humongous Mecha (Lots, Gunzack in particular), Implacable Man (Blockah Boyz), Gatling Good, Chainsaw Good, Tank Goodness, Lightning Bruiser, Roaring Rampage of Revenge, Living Weapon (Most Black Pikmin count), Spikes of Villainy (Love 'em), Badass (Most such tropes are covered), Berserk Button (Kill a Black Pikmin. Observe the reaction of any others nearby), Bling of War (Da Boyz do love their flashy bitz), Bloody Hilarious, Gadgeteer Genius (Mek Boyz in general can instinctively build most forms of mechanical weaponry), A Team Firing, Screaming Warrior (Boy howdy), The Scrounger, War is Glorious, Mood Whiplash (Their antics can be pretty funny, but one would do well to remember that they're mass murdering psychopaths), Ground Pound (Storm Boyz love this)