1. Red-Headed Step Child, PG, by snickfic. The story of how Abaddon became the sole knight of hell (though the author takes a couple liberties with the vocabulary.) It's rare that I find Abaddon fic that isn't bump-n-grind oriented, and this was a really elegant, really lovely read that also gave some intriguing theorizing on Hell's power structures.
2. Such Good Boys, NC-17, by teaandchess. The Dean/Abaddon/Sam sandwich that everybody knows they wanted. Jesus fucking christ this fic is hot. Lots of sniping banter and Winchesters taking Abaddon apart (sexually, not literally this time.) Me gusta!
3. Run The Streets Red, R, by variouslygarnished. Oh oh oh, Kali/Abaddon. When I say this pairing is awesome, I mean in the biblical way, not the Dean Winchester way. It is inspiring of awe. This is a oneshot on how an alliance is made between two destroyers, and it's absolutely flawless.
4. Objects in Motion, NC-17, by cadignan. It's smutty and it's angry and it's all the vicious power struggle you could expect between Naomi and Abaddon when they get it on in a sexy PWP. I love Ray's work because even when it's 1k of porn the characterization is so freaking spot on I could die.
5. Queen of Hell, R, by amicalement. A coda to 8.22 (that has sadly become canon divergent), where Abaddon raises a little hell and kicks a lot of ass. Very bloody (which admittedly I am kind of a sucker for), and very satisfying, since Abaddon basically guns straight for Crowley in it.