Unlike most KX-series droids who were effectively emotionless, K-2SO's reprogramming led to the development of a fully self-aware personality; he was cynical, blunt and did not hold back his opinions, but he was well-meaning and honest. He was also prone to sarcasm and stoic, often mentioning that he had calculated the poor odds of success in any given situation (which Cassian Andor would then refuse to hear). His sarcasm extended to the point where he would disobey minor orders and prove his ability in given missions, as seen on Jedha. K-2SO was fairly independent and frequently disobeyed orders he felt were counterproductive, scolding his organic compatriots for ignoring his advice. He genuinely regarded Cassian as a friend, however, K-2SO was selfless to the point where felt no hesitation in sacrificing himself in order to protect him and Jyn Erso during their mission to steal the Death Star plans.
Powers and Abilities
Droid Strength: As a droid, K-2SO was physically stronger than most other sentient beings.
Droid Durability: As a droid, K-2SO could take far more damage than most other sentient beings.
Master Analyst:' Despite not being an analyst droid, K-2SO could estimate if his allies' tactical strategies were 97% or 100% effective; it was likely that he was programmed with this feature, by the Rebel Alliance.
K-2S0 first appears to rescue Jyn Erso from an Imperial labor camp on Wobani. He accompanies Cassian and Jyn to find Saw Gerrera on Jedha, who had been close to Jyn's father Galen.
On Jedha he is told to stay with the ship, but later reappears to help Jyn and Cassian to fight off Stormtroopers after Saw Gerrera's henchmen make an attack on an Imperial cargo transport. He later helps them out of Jedha.
On Eadu he is told to stay with the ship, which he does. He later agrees to accompany Jyn to obtain the Death Star plans, and on Scarif imperial base he communicates to Cassian and Jyn the location of the Death Star plans in the control room. Jyn gives him her blaster before attempting to steal the Death Star plans. He tries to fend off attacking Stormtroopers but eventually succumbs due to multiple shots from them.