I don't have a problem with the actual kill; regardless of it being too soon in Superman's tenure it was a situation where he had no choice. Zod forced his hand. My problem was the lack of proper context in the whole situation. The amount of death and destruction that occurred just prior is barely addressed by Superman so the fact that he appears so distraught over the possible extermination of a single family is inconsistent. Maybe he did care immensely but there is no recognizable indication.