Informed Flaw: Mike's joints are said to be bad, which forced his retirement from the SEALS, but other than brief mentions, particularly when first starting up in the morning or after significant periods of sleep, it doesn't seem to really slow him down all that much. Of course, the real reason he retired was political; see Retired Badass.
Not So Different: Mike believes himself to be a rapist at heart (at one point in Ghost, he treats a Serbian prostitute very roughly, but he is very remorseful about it later, buys her freedom from her pimp, and helps her get a new life in France), but he channels his darker urges into BDSM activity with consenting partners and holds himself to a strict Warrior Code. When he encounters men who don't restrain their baser impulses, copious bloodshed ensues.
Reality Ensues: Mike's been shot, blown up, cut, and got the bends and hypothermia in an unpressurized nosewheel compartment at high altitude. Getting out of bed in the morning is a twenty-minute ordeal of painfully forcing his fucked-up joints to work again.
Retired Badass: Former Navy SEAL supposedly medically retired due to injuries; when he was first transferred from training to a Team, he pointed out some Reckless Gun Usage, but was ignored. The resulting "accidental weapon discharge" resulted in a wounded operator, but the team closed ranks around the guilty party. The brass was forced to choose between an untried newbie and an experienced team, and showed Mike the door. The medical discharge was just someone's way of acknowledging Mike wasn't at fault and sparing him from dishonorable discharge.
Freudian Excuse: Katya was born to a dirt-poor Russian family who sold her into prostitution when she was eleven. She got passed around from one pimp to another in Russia and Ukraine for the next six or seven years before finally ending up in northern Georgia. Given that her previous pimps rented her out to the kind of people who like having their way with pre-pubescent girls, it goes without saying that she didn't have a happy childhood. She's been raped and abused in unspeakable ways in the past (at one point she remembers a Japanese businessman who forced her to eat his shit). No wonder she's such a bitch.
Omniglot: Russian is her first language, also fluent in Ukrainian and Georgian. She picks up English pretty quick, and even manages to get rid of her Russian accent and pass for an American party girl in A Deeper Blue.
Took a Level in Kindness: Following the events of Unto The Breach. She's still no softie, but it seems that watching people die in the process of helping her out of a bad situation mellowed her somewhat, though Jay still points out that she has almost no ability to empathize with others.
Waif-Fu: Call it what you want, it's pretty effective while her combat drugs last.
You Wouldn't Like Me When I'm Angry: Thanks to some surgical enhancements by a CIA doctor, courtesy of Mike pulling some strings, when Katya really wants to make somebody die horribly, she can activate a refillable reservoir implanted in her chest that dumps multiple "combat drugs" into her system, putting her in an artificial Rage Mode. For the next ten minutes, she possesses heightened senses and reflexes, otherworldly speed, and surprising strength. The retractable claws in her fingertips and poison injector in her hand are a nice bonus. Sure, it only lasts ten minutes, but she won't need that long. Whoreverine indeed.
Too Kinky to Torture: High-level BDSM sub who complains that Mike doesn't whip her hard enough. When a drug lord tries to interrogate her, she merely finds his abuse moderately arousing.
High Priest: Of the Keldara's pseudo Norse/Celtic religion. One of the reasons why he's been hanging on to his role as a Father and clinging to life for so long. Before Mike came along, he was one of the last living Keldara who had actually been to war, and their traditions state that only such a warrior could lead the Keldara in their rituals.
Reasonable Authority Figure: His travels have left him a bit more flexible than the other Elders, particularly the grouchy Devlich and stiff-as-a-board Ferani. He's also more willing than most to put up with the occasions where Mike's edicts clash with Keldara tradition because he sees those changes as acceptable hurdles in the name of restoring the Keldara's status as warriors.
Dumb Muscle: The Keldara think his mother dropped him on his head as a baby. When Adams is trying to teach him to breach a room, he has trouble getting through Step One, "take five steps forward," because he can't really count that high. He's described as an absolute savant with heavy weapons, though, particularly his beloved rocket launcher.
No One Could Survive That!: After taking the brunt of an explosion that nearly killed Chief Adams, Shota regains his feet and complains only that he "Doesn't like doors anymore." Adams's incredulous response is, "Holy shit, you're ALIVE?"
An Axe to Grind: Leads the Keldara women in a wild, guns-blazing charge against Chechen emplacements to free up an escape route for the men and uses a hand axe, leading to...
And Show It to You: Executes one of the surviving Chechens by using her axe to chop his chest open so she can pull out his heart. His last view is of a bloodsoaked Lenka dribbling blood from his heart into her mouth.
Cool Old Lady: By far the least uptight of the Keldara elders, with a bawdy sense of humor highly unusual among the prudish Keldara. The other Keldara half-jokingly say that she's a witch.
This is at least partly because she's only Keldara by marriage. Mother Lenka is Russian, born and raised in Leningrad (implied to have made her living there as a prostitute), who came to the valley in 1945 as a now-deceased Keldara soldier's war bride. Nevertheless, she's thoroughly devoted to her adopted people.
High Priestess: Known only to the women, since they have a set of rites considered secret from the men, with Mother Lenka as their current leader.
First Girl Wins: Averted; though Katrina is the first Keldara Mike encounters, and though she spends much of the second and third book trying to win him over, he's just not able to get over her young age. By Unto the Breach, she has begun diverting most of her energy into being Mother Lenka's apprentice and seems to have largely given up on Mike, particularly once it becomes clear that he's hopelessly obsessed with Gretchen.