At first Rick does not feel anything towards killing androids,
"The electric animal, [Rick] pondered, could be considered a subform of the other, a kind of vastly inferior robot. Or, conversely, the android could be regarded as a highly developed, evolved version of the ersatz animal. Both viewpoints repelled him." Ch.4
After retiring his first three Andys, Rick begins to feel something is not quite right. The zeal he once felt is not there in the same way. He does not look forward to his next kill. By chapter 12, Rick confesses a difference between himself and Resch,
"The way you killed Garland and then the way you killed Luba. You don't kill the way I do; you don't try to—Hell," he said. "I know what it is. You like to kill. All you need is a pretext. If you had a pretext, you'd kill me."