Koba was an altered bonobo with a strong hatred for humans, stemming from years of neglect and abuse. He had a scar over his blind eye and looks more feral than the other apes held at Gen-Sys Laboratories. Ten years after escaping the Gen-Sys Laboratories, Koba became a member of Caesar's colony of 2000 apes.

Koba, traumatized and disordered by the experimentation he received, was psychologically defeated and extremely vengeful with a bitter vendetta against humans, notably Steven Jacobs. Malakai Youmans noted that Koba's neutral expression was identical to those he'd seen on the faces of child soldiers he'd encountered in Central Africa. Highly intelligent, callous and bitterly selfless, Koba enacted his vengeance against Jacobs at the climax of the Battle on the Golden Gate Bridge, by brutally killing him without saying a word and a mere, adamant and malevolent glare flashing in his eyes. He was also short-tempered, aggressive, ruthless and had a strong hatred for humans.

Despite his past experiences, Koba did have a kinder side. He served as a mentor to the younger generation of apes, especially Blue Eyes and Ash, the sons of his friends, Caesar and Rocket. He was also kind to many of his fellow apes, including Maurice of who he offered fruit to during the early days before the village was established. However Koba's hatred for humans eventualy went too far when humans were rediscovered 10 years after the Battle on the Golden Gate Bridge. His actions result in a war against humans that also harm his ape breathren.