In Season 4, Stan and Xev begin using the world "evil" a lot, in a very juvenile-sounding way. For example, telling Prince they won't make a deal with him because "We're not evil like you!" or exclaiming, after 790 destroys earth, "790 you are so evil!" Why do they seem to be using the word "evil" like children? Because it's a new concept to them. And in many ways, the protagonists of "Lexx" are children, mentally. At the start of the series, they'd all emerged from very isolated lives, spent in an entire universe ruled by an evil empire. Empathy and compassion were never taught to Stan, Xev or 790, and Kai's heroic morals were erased when he was made into a Divine Assassin. They start Season 1 with their morality as completely blank slates, and only through their experiences start to gain a sense of good and evil. They start as cowardly, self-serving antiheroes, but by the end, have been transformed pretty much into traditional heroes.
More Fridge Brilliance, for Zev/Xev Bellringer. She may have been cowardly and selfish in some ways at the start, but she seems to have been born with a natural kindness that is never erased by any amount of hardship or brainwashing. We see several examples of this.
A flashback in "Supernova," showing Zev's childhood at the Wife Bank. We see the holographic teacher give Zev a multiple choice question, concerning what to answer to a husband who asks if he's fat. Her first guess is, "It's not what's on the outside, it's what's inside that counts." The wife bank, of course, tells her she's wrong, and the "real" answer is something superficial. The point is, Zev thought of that response on her own, as a child, with no one to teach her about inner beauty.
In "Midsummer Nightmare," when King Oberan brainwashes Xev to fall in love with him, his brainwashing isn't complete. He does succeed in making Xev want to marry him, after she venomously refused before. But she still insists that he free her friends, and "be nice to Titania!" Later, as a brainwashed tree singing in Oberon's praise, Xev stops her singing to comfort a crying Titania.
790's descent into psychotic, murderous villainy does make sense when you look at the factors. In the first two seasons he was in love with Zev/Xev who was an affectionate person, who carried him around almost everywhere, gave him frequent compliments and physical affection and was quick to shut down anything more aggressive than a moderate insult. In the last two seasons he's bound to Kai, who lacks emotions, motivation and the ability to react to context. As such he ignores 790's needs, leaves him alone for long periods of time, never gives any demonstration of affection unless specifically asked for it, and even then didn't always do it, and denied any affection for 790, due to being dead. Kai basically spent the third and fourth season emotionally abusing 790, accidentally of course, and 790 suffers noticeably for it. Add in that Xev was mortal and therefore killable meaning having others around to protect her, or at least act as meat shields gave 790 a reason to keep other people around and occasionally show the slightest bit of gratitude towards others for saving Xev, whereas Kai was basically indestructible so no other beings were necessary for his continued survival.
The three ersatz American astronauts from Potatohoe are all killed by Lyekka—pronounced the same as the Soviet space dog. Becomes doubly funny when you consider "Girltown", also written by Lex Gigeroff, has an explicit pro-socialist message.
From the start of Season 3 and onward, all of the people who Stan reminisces about—his brother, the best friend he betrayed at age 14, etc.—are all dead, because the Light Universe was destroyed, and even if he didn't, he spent 4000 years in cryo sleep anyway.
The love slave transformation machine is obviously already horrific but there is a layer of Fridge to its implications as it is a two-part process: body first then mind, with the mind part appearing to be completely optional. This means that everyone in this universe could be young, beautiful and healthy - the ruling class just doesn't want them to be.
It makes complete sense that the Love Slave programming would make the slave obsessive to its mate, but 90% of what makes up 790's character makes no sense. There's no benefit of a Love Slave that actively hates and wants to kill everyone but its mate.
