Nearly Destroyed Chapters
While certain Space Marine chapters have been utterly annihilated with no hope of being rebuilt (though some hope of being re-founded) there are also several chapters that have been badly depleted but who are still kicking. This page aims to shed light on these chapters as they make fantastic army modeling ideas; everybody loves a wounded hero, and hey, it's feasible to collect the ENTIRE chapter.
Note that some of the chapters previously listed here have been Primaris-ified up to full strength again (Yippee!), and thus have been taken off the list.
Get their shit handed to them by *cough* Ork Snipers *cough*, for having the balls to tell the Inquisition to fuck off. Currently lost all their officers and apothecaries, and rely on Black Templar apothecaries to rebuild their numbers. This means there are a lot of Black Templars among them and then the Ork Snipers decided to trick the Mentors chapter in order to openly assassinate the leader of the surviving Celestial Lions. So, the Black Templars, the Mentors, the Celestial Lions, and probably the entirety of Dorn's legion and maybe the Custodes have been pissed off by the Inquisition and Assassinorum. On top of whatever Guilliman is going to think when someone inevitably informs him.
Lost like half of their chapter when they (successfully) tried to solo an entire fucking craftworld. Well, a damaged and partially nommed craftworld, but still, impressive. Then the other Eldar invaded and purged their homeworld, wiping half of the remaining chapter. Few years later Invaders engaged in the World Engine conflict and lost two full terminator squads and probably few ships. While some other chapter might get the message fate keeps slapping them with and try to rebuild their numbers for a decade or two, the Invaders continued to jump into trouble like they heard the universe was handing out asses and they've known nothing but years of bitter ass-famine. They would continue to charge into danger and get their butts handed to them until they eventually walked into a trap set by none other than Ahriman himself. Only thirteen or so Invaders got out alive, and even then only thanks to some help from the Grey Knights. The thing is, though, that though they get their butts handed to them constantly, their enemies usually come off far worse for it. Defeating them is generally a phyrric victory and it doesn't take long for them to rebuild their numbers enough to keep doing their crazy thing.
Although their chapter isn't far from full strength all their geneseed got stolen Blud Rahvens style by the Red Corsairs. Huron Blackheart baited them with a fake invasion attempt and then attacked their chapter fortress while the fleets were away. So now they are doomed to slowly die from excessive power-facepalming. Though it's likely to recover gene-seeds from their existing marines, the process of rebuilding their stocks to their former quantities is no doubt a long and perilous path, especially if they don't want it stolen again.
The Raptors chapter has elevated near destruction into an art form. They've lost their homeworld, their best wargear, countless companies, and eventually even their taste for flashy, bullet-attracting paint schemes. They've been declared dead by the Administratum as often as Ciaphas Cain, and every time they eventually reappear, even more sneaky and reasonable than ever. Unlike other chapters, the Raptors actually learn from their mistakes. Every time they avoid total annihilation brings them closer to their true form: Tanith Marines.
The story of HOW they get so mega-fucked is the plot of several novels, but at the end there's only three left who are still loyal and those guys aren't coming back anytime soon. Long story short, cursed and declared heretics, decided to go down fighting Chaos rather than the Inquisition, all except one traitor and three loyalists died in the fighting and then the three loyalists dragged the last traitor to the Warp with them, absolving themselves in the eyes of their (official) parent chapter.
There have been reports of Chadmarines using their name and livery, but whether or not they're descended from the original Soul Drinkers is debated...