"The red dragon who made a pact with Caim is an exception among exceptions. Caim and the dragon met while both were on the brink of death. At the time, Caim's heart was filled with a strong desire for survival, fueled by a desire for revenge, and it was this negative emotion that captured the heart of the 10,000-year-old dragon. Since dragons are unisexual and have no gender, this could be considered a proper case of 'love.'" - Drag-on Dragoon Perfect Guide pg 22

“The dragon has never felt anything but scorn for mankind. But as she flies, she begins to feel strange new emotions for this man called Caim. Now, they fly to the city. To Manah. To revenge.” - Drakengard 1 - Verse 3: The Capital

Drakengard is a beautiful love story between a mute murderous psychopath who hates all of humanity and kills children and is so obsessed with bringing destruction and death to the world he continues to attack and destroy corpses even after they're dead and the only sounds he makes is grunts and snarls, and his dragon wife Angel(us) (her name depends on the translation, she's Angel in Japanese, Angelus in English. She's also voiced by Caim's voice actor in Japanese while in English she has her own VA, Mona Marshall) who is somehow the more sane of the pair despite also despising humanity. Also some other guys are there, like Aurioch, the woman who murders and eats children after losing her own in a violent and traumatic slaughter, Leonard, the blind paedophile whose 3 younger brothers (who he was sexually attracted to) were killed by the Empire after Leonard left them alone to go jack off to them in the woods, and Seere, a spoiled child who's permanently six years old and commands control of a golem with unimaginable power and is also the brother of the six year old leader of the Empire. There's also Furiae, Caim's sister, who is incestously in love with Caim, and when he reacts with disgust and rejects her advances, she kills herself, which is a Mega Problem as she's also the living seal of the Goddess that stops the world ending. And Inuart, Furiae's fiancé, who loved her madly but harboured a hatred for her brother for stealing her affections, a hatred which eventually manifested in him joining the Empire and selling his soul to Legna (yes, it's Angel backwards), the black dragon who killed Caim & Furiae's parents (the King and Queen) and started the war in the first place.
Probably the two most "ethical" or at least vaguely honourable characters are Leonard and Seere, which... you know the cast is fucked up when the paedo is the most reasonable and sane one there.

“According to Taro Yoko, Caim was conceptualized at the same time as the Red Dragon. The development team wanted to create a "new type of romance" between an elderly woman and a young man and purposely cast them with the same Japanese voice actor”

“For the first time, tears are shed. For the first and final time, love is confessed.” - Drakengard - Chapter 8, Final Verse

“To Angelus, Caim is a constant surprise. Fascinating, provocative, and one of a kind. She does not realize that her feelings for him are similar to love.” - Drag-on Dragoon Official Guidebook Complete Edition, pg. 34

“[Caim's] feelings for Angelus remain unchanged as he is driven to desperation, feeling her pain through his pact with her, and is willing to condemn the world to chaos to end her suffering. In the end, he accepts his death in order to be with her again. ”

“Caim - Silent math teacher who is known for his radical teaching method of only writing on the blackboard to communicate to his students. Rumored to have been married to Angel. Angel - Mysteriously appears before Nowe before the school culture festival. Woman agent wearing a red mask. She climbs on the rooftops of nearby buildings to observe the school. Looks young but speaks with an archaic tongue. Apparently frequents the convenience store but has trouble using microwaves. She often asks Caim to use them for her.” - Angelegna DOD Alternative ~Fuuin Gakuen~ (エンジェレグナ DOD ALTERNATIVE ～封印学園～)