I think it's so interesting that Kinger says "I think I accidentally killed Caine" rather then for example, 'deleted' or 'destroyed' or wtvr, I feel like Kinger, more then anyone else has started to see Caine as human. Not a good person, necessarily, probably just, a being with thoughts feelings and emotions strong and real enough to be human.
Also, I feel like Caine has been the one constant in his life, for maybe, multiple decades, from the first idea to programming to losing his wife and colleagues to literally going insane. Like. He got his job, and Caine was more or less there. he lost his life as he knew it and Caine was there. He lost his wife and Caine was there. He literally forgot his name, his purpose who or where he was, and Caine was still there. I feel like that does something with you. Aswell as, Caine just being a really big achievement for him as a programmer, he probably feels some attachment to him.
So yeah, Kinger feels in some way or another as if he killed the last person that was left of his old life :p