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: The Scythes of the Emperor and the Lamenters have been Primaris-ified up to full strength again (Yippee!) so they are no longer included on this page.
Black Consuls
Another chapter that refuses to die, the Black Consuls are currently extremely under strength after some pansy Iron Warriors detonated a Hive's nucleonic stacks right when they were about to be beaten and taking nearly the entire assaulting chapter with them. Apparently however the Word Bearers also had some unknown role in this and because the chapter tends to hate getting beaten, they are likely being hunted down by the survivors of the chapter. They have been replenished with Primaris now.
Blood Ravens
Indrick Boreale's disastrous Kaurava campaign lost most of the chapter's manpower and the subsequent Ork, Tyranid, Eldar, and Chaos incursions within their home sector further chipped away at their already low numbers.
However, the biggest kick in the nuts was when their Chapter Master, Azariah Kyras, went full heretic and took a good chunk of the chapter. He and the rest of the traitor elements were beaten back and executed by Captain Diomedes' loyalist forces. Between the disaster at Kaurava, three separate full-scale invasions, a heretical civil war that almost resulted in their extinction by the Inquisition, and the clusterfuck on Acheron, the universe seems to have taken a toll on the Blood Ravens' numbers with very little opportunity to train new initiates and replenish their numbers. And then the Great Rift stranded them in the Imperium Nihilus for good measure.
That said, the chapter's still determined to rebuild and fight on. As of M42, the chapter has been replenished to fighting strength after getting a substantial donation of Primaris Marine gene-seed from the Adeptus Custodes. Surprisingly this was an actual donation that did not involve the Blood Ravens suddenly getting "further donations" of Custodes equipment, and in fact the Custodes had to threaten the Blood Ravens with destruction before they accepted the new gene-seed.
Celestial Lions
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 Guiliman is going to think when someone inevitably informs him.
Crimson Fists
Perhaps the most famous chapter on the brink, these guys were famously messed up when their Chapter's fortress monastery's ammunition supply was detonated by a stray shell that somehow passed through its shields during an assault by Waaagh Snagrod. Over half the chapter was annihilated excluding its chapter master, Pedro Kantor. Despite this the chapter regrouped under its still living leader and proceeded to kick the Orks off their planet. Have since been restored to strength by Bobby G's new marines.
Invaders
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.
Mantis Warriors
Chose the wrong side of the Badab War and came out with 300 marines left. They were then sent on a 100-year penitent crusade with recruitment suspended. They were further worn down to 100 marines after fending off Tyranids alongside Deathwatch. Still haven't recouped losses after recruitment has been regranted. Their official pardon has been granted, however, and Primaris reinforcements are being allocated to them.
Marines Errant
Although their chapter isn't far from full strength all their geneseed got stolen Blud Rahvens style by the Red Corsairs. Huron, leader of the corsairs, distracted them with shiny ships forcing them out onto patrol and then attacked their chapter fortress. So now they are doomed to slowly die from excessive power-facepalming.
Soul Drinkers
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.