Koli experience life with the same parents of Kilo and lost them in the same way. He fell in love with Charlotte just the same as Kilo. However, rather than allowing Charlotte to die when attacked by Saitaron, Koli slays her assaulter and gets her a healer.
He was still late for that date with Charlotte however, and to make up for that, Charlotte demands food. Lots of food. A feast fit for kings. And Koli spends every last bit of money he could get to fulfill that wish and be forgiven.
The following day, Charlotte died of food poisoning.
Koli beats himself senseless for losing her- not unlike Kilo- but has to deal with associates of Saitaron whom are trying to kill him for various reasons. With all the blood he sheds, something snaps in Koli's mind that morphs him into a twisted state of perception that views everything as led by life, death, and pain. Life and death being necessary for the other to continue, and pain giving either of those things meaning. (If you felt no pain for the loss of life, then naturally it would not be a problem to you to have someone you love die. If people felt no pain throughout their lives, they would very seldom be motivated to keep living.)
Pain being the cause of every problem than he'd ever known, he dedicates the remainder of his life to ceasing pain and 'perfecting' the world by ridding it of all things that may cause pain. Including the living creatures that experience it. It is in this manner that he feels he is obligated to kill everyone or put them all to sleep- he can find no other alternative to create a permanent end to the suffering.
However, because of this he is inspired to travel across the lands surviving by any means while ending the pain he can on his path. Because of this difference from Kilo, who leaves Tek for the Chuian Tree after Charlotte's death, Koli never met and killed Amelia, but rather drugged her and abused her in her drugged state. As he did with most Chuians he encountered. He never forms a relationship with Mia and he forgets what it means to love another being, and seeks his goal of ending all pain with every bit of his life.