Ragnar Blackmane
Ragnar Blackmane, also called the Young King, the Gifted One, or the Allslayer, is a goddamn beserker killer werewolf of the Space Wolves Chapter, and the only Space Wolf approaching Mary Sue levels of ridiculousness.
Somewhat uniquely, he also has six different books, which don't necessarily fall into a particular series. Four of these were written by William King (of Gotrek & Felix fame), while the other two were written by "Lee Lightner," a pseudonym for two separate guys.
He also lived on Holy Terra for a few years, as well as having an absolutely ridiculous amount of plot armour.
The Books
Space Wolf: This book covers everything about the recruitment and training of the Space Wolves, as seen through the perspective of Ragnar. It starts with Ragnar still a Fenrisian tribesman. After some viking-related escapades (including the death of his father and sexy time with a viking chick), Ragnar goes batshit insane and kills tons of rival tribesmen. This causes the Wolf Priests to show up and recruit him. Then a drill sergeant named Hakon yells at him a lot. The book concludes with his first assignment as a Space Wolf, in which he and his buddies stop a Chaos invasion single-handedly, using nothing but plot armour. Ragnar even kills a Chaos Sorcerer named Madox.
Ragnar's Claw: A friend/ally of Great Wolf Logan Grimnar (who is, inexplicably, an Inquisitor) shows up and tells Ragnar to help rebuild an amulet. A love interest (who happens to be a psyker) dies to imprison a Greater Daemon of Nurgle. Entertainingly, Ragnar gets pissed on by a drunk Ork.
Grey Hunter: The Thousand Sons decide to repay the Space Wolves for Prospero by defiling a sacred planet. Naturally, this pisses off the Wolves. Due to his plot armour, Ragnar kills Madox (again) before throwing the spear of Leman Russ through the eye of Magnus (yes, Daemon Primarch Magnus).
Wolfblade: Ragnar is banished (but only for a little while) and forced to protect a Navigator house named Belisarius. Why? Because he threw the most sacred relic of the Wolves into the Throne-forsaken Warp. This leads to much dicking about on Terra as well as massive amounts of just as planned.
Sons of Fenris: There's a war between the Dark Angels and some balls-of-steel PDF troopers on a promethium-filled Death World called Hyades. Ragnar gets involved in some just as planned in the jungle.
Wolf's Honour: There's more Inquisitors, some Daemon Worlds, Wulfen, and a planet called Charys that's going to get BLAMmed. Basically, Ragnar tries to steal the spear of Russ back and, in doing so, pisses on centuries of Magnus' just as planned.