Badass Decay: The Lessening Society in general, as of the last two or three books. As the focus has shifted to Xocr and the Band of Bastards as the new threat to the Brotherhood, they've gone from being a well-organized, professional force of supernatural killers to a loose band of psychopaths led by someone only ever referred to as "Little Shit". Oh, they're still a threat, of course, but not nearly what they were at the beginning of the series.
Although, it is stated that the war ebbs and flows like that, and has done throughout history. However, with Butch being reborn as the Dhestroyer and Xcor wiping out every Lesser in England and perhaps beyond, the Omega is certainly on the run by this point.
Taken a bit literally with Lash. After his resurrection is complete and he becomes the head of the Lessening Society, in Lover Mine he begins to physically degrade into a zombie-like slime creature until he's finally put down by Xhex.
Throe, as of The Beast and The Chosen. Once he was a savvy politician within the glymera and gave the Band of Bastards an in with the aristocracy to unseat Wrath. Now he's couch surfing with young ladies in exchange for sex and money. He has resorted to mysticism and spellcraft to try and rebuild his power base. He even lampshades this fact as he enters a human psychic's shop.
Phury and Rehvenge kiss in Rehvenge's office, though it is played more as a dominance thing than actual attraction.
Recently, Qhuinn and Blay, and Blay and Saxton.
V and Butch have skipped way past mere Ho Yay in Lover Unleashed.
Wrath once kissed Rhage on the forehead, as a token of respect apparently.
The Omega rapes his male recruits as part of their induction into the Lessening Society. At least one of said recruits is implied to enjoy this.
There's a missing segment cut out of the first book because Ward's publisher's felt it was too controversial to include. It consisted of the then-Forelesser Mr. X going to his young recruit Billy——who had been explicitly stated to have just turned 18 like a week ago——and proceeding to reach into his pants and stroke him to orgasm.
Moral Event Horizon: Qhuinn's behavior in The Chosen crossed this line for a lot of fans. Within the space of two chapters he:
Tries to strip Layla of her rights to see their twins, Lyric and Rhampage.
Fires a gun within the twins' nursery while the twins are in it.
Tells Blay he is not a parent to the twins when Blay tries to play peacemaker between Qhuinn and Layla.
And later, he can't bring himself to touch or look at Lyric because she looks too much like Layla.
Tear Jerker: Wellsie, her unborn son, and her cousin, Sarelle, are slaughtered by the lesser Mr. O in Lover Awakened.
Bitty's entire backstory in The Beast. A physically abusive father, a mother who dies from the injuries inflicted by said father, and a life growing up in seclusion and poverty made Mary's attempts to reach out to her all the more tear-inducing.
Taken Up to Eleven in Blood Vow. Bitty's father broke her bones so badly that Havers must manually break and reset the bones in order for her to have a chance of walking when she completes her transition into an adult Vampire. And it has to be done without anesthesia.
Jane being murdered in Lover Unleashed and Vishous's desperate flight to save her was this Up to Eleven for some readers.
When it seemed like Xhex was going to die as Lash's prisoner after the Brotherhood had found where she was being held but had no idea she was still there thanks to a barrier which trapped her in a Pocket Dimension as if she was a ghost.
Pretty much par for the course of the BDB series. Each book will contain at least one monumental Tear Jerker.
They Wasted a Perfectly Good Plot: During The King while Beth is recovering from childbirth/hysterectomy, within one chapter Wrath announces that he's reformed the entire Vampire political structure from a monarchy to a democracy, held elections, and he was selected to reign as King for life. A plot that could have been several books on its own happens from one chapter to the next just after a bloody and emotional childbirth scene.
"Actually... I abolished the monarchy last night... Also the glymera are out of a job."
Win Back the Crowd: The Legacy series seems to be an attempt at this. Introducing a whole new caste of characters to bring in new readers while sprinkling in the original couples as a lure to those who dropped out of the series. Based on book reviews, it seems to be winning readers back!
Why Don't You Just Shoot Him?: Seriously, why do the Lessers even bother trying to throw down with blades or clubs or hand-to-hand with the Brotherhood? Centuries-old warriors that have mastered most forms of combat, and the pale boys go in for fisticuffs. So why not invest in some cheap Glocks and just shoot them?
That is indirectly explained in the books. It's mainly because they don't want to draw attention to themselves and shoot-outs in alleys and abandoned buildings are not a good way of keeping a low profile. If the Lessers can do it without drawing attention from cops or other humans then they'll do it, but keeping the war secret is more important than the advantage using guns all the time would give them.