Ogryn Brute
Ogryns are dumbasses. Unfortunately they're such dumbasses that sometimes they don't even know they're fighting for the wrong team. This is where Chaos Ogryns or Ogryn Brutes comes in. Chaos renegades are quick to forcibly conscript them into their ranks and doing so is pretty damned easy. They just tell the Ogryns that the new Gods they are fighting for is instead another variation of the Emprah. To make them more lethal, the renegades use crude surgical procedures, combat drugs, and sorcerous rituals to control the beasts and set them upon their enemies. Modified and warped by forbidden methods, the Ogryn Brutes can be split into two varieties, these include Ogryn Berserkers and Plague Ogryns (presumably because they are too stupid to worship Tzeentch, though they'd likely still be found as Slaaneshi due to gluttony fitting excess, the existence of Malal Ogryns is still up for debate.)
Ogryn Berserker
Ogryn Berserkers are Ogryns corrupted by Khornate Chaos Warbands, a combination of the Ogryn's simple-mindedness, strength, and Chaos' natural ability to turn it's followers completely insane has turned these Ogryns into absolute murdermachines of pure, fanatical hatred.
Unlike their power-armored brethren, brutes have been completely lobotomized, preventing any kind of higher thinking or reasoning and basically turning them into an even more horrific version of the Imperial servitor. As a unique feature: their bodies are injected with a drug called "Slaught" (the followers of Khorne aren't known for being creative). Slaught increases the Brute's aggression to absurd levels, turning them into essentially a hulking, angry meatgrinder who's sole purpose is to kill with extreme prejudice. The downside is that Slaught wreaks havoc on the Ogryn's body, and prolonged combat will eventually kill the brute.
In order to get most of their money's worth with their suicide berserker, the masters of brutes typically augment their creations' killing power by sticking as many blades and pointy sticks on them as possible, removing limbs and replacing them with crude but effective weapons if necessary.
Plague Ogryn
As sturdy abhumans that can rival the strength and hardiness of space marines, it wasn't a surprise for the likes of Nurgle to take special notice. Originally created from the experiments on captive and rebel Ogryns from Vraks by a Nurgle warband known as The Tainted; Plague Ogryns are some of the newer and terrifying servants of Nurgle. Unlike the Berserker, Plague Ogyrns have been mutated to the point of non-recognition, resembling a miniature Great Unclean One or an ogryn-sized Nurgling more than the ogreish brutes they were based on.
As you can expect, these mutations have turned these stocky abhumans into near-invincible disease vectors, their huge bulk and natural hardiness allows them to host countless numbers of plagues and diseases to fester within their bodies. Due to this, getting so much as scraped by these things is a guaranteed one-way-ticket to a most painful end best not described. A particularly gruesome side effect of all the filth and disease built up inside of their bodies is they tend to explode in showers of pus, spores, and flies when killed; while fellow Nurgle worshippers enjoy this it can be quite fatal for anyone else.
After Vraks, its speculated by the Ordo Malleus that The Tainted have been further refining their creation of Plague Ogryns to be even more potent than they already are. Additionally, as the newest hip thing and having a live demo in Vraks: Nurgle warbands have been seeking out The Tainted for an opportunity to obtain these creatures, of course in exchange for slaves who have the unenviable role of being test subjects for The Tainted's experients.
Tabletop
Ogryn Brutes, whether vanilla, Khorne or Nurgle affiliated, are tough motherfuckers. They are essentially Chaos Spawn on steroids-OHGODNOOOOOOOOOAFBKDNOANJDJALIJDOASASDAARRRGHHH!.... *BLAM* continuing on from my predecessor, each Brute is Fearless, with Hammer of Wrath and Rampage, which means with their base D6 attacks, you could potentially have 11 attacks per model on the charge. One brute can be upgraded to a Packmaster, which loses Rampage, but allows you to take up to 6 Chaos Hounds, which has some impressive combat stats (WS3 S5 T5 W2 I4 A3), and they allow you to roll 2D6 picking the highest for Sweeping Advance. They can be dedicated to chaos gods for about the price of a typical power fist, giving them either 2D6 picking the highest for their attacks (Khorne), Feel No Pain (5+, Nurgle), Fleet (Slaanesh), or an additional close combat weapon with Soul Blaze (Tzeentch). Additionally for a flat rate, you can give the squad Flak or Carapace armour, which means with Nurgle, they could be quite tough to kill. Overall, while a squad of 5 Nurgle Brutes with Carapace armour is looking at a whopping 360 points, but they’re likely to wreck anything they make it into combat with.