Few characters in the DC Comics pantheon embody the ideals of morality and virtue more than Superman. Acting as the universe's moral compass, the Last Son of Krypton is humanity's shining beacon, which makes it all the more shocking when Superman is forced to kill.
And it's not just in the comics that Superman has had to take a life or two. Due to his Boy Scout reputation, casual fans may have been a little taken aback to see Superman snap General Zod's neck with his bare hands at the end of 2013's Man of Steel. But the truth is that Superman had already killed Zod in the comics decades beforehand, and he did it in a much more twisted manner.
In 1988's Superman #22 - from John Byrne, John Costanza, and Petra Scotese - Superman is in a pocket dimension in which General Zod and his cohorts Quex-Ul and Zaora have decimated that version of Earth, killing billions in the process. After depowering the trio with gold kryptonite, Superman declared that it's his duty as, "judge, jury... and executioner" to dole out their punishment. He brandishes a jar of green kryptonite in front of his depowered foes as they scramble for their lives. Zod tries to blame his compatriates for their plan, leading to Quex-Ul strangling him. Meanwhile, Zaora basically offers to be Superman's sex slave in exchange for her life. All the while, Superman silently stands there and watches until his enemies perish.
It's a jarring scene and one that shows just how much Superman's characterization has changed throughout the years and across different media. Henry Cavill's Superman is devastated after having to end Zod's life, almost as if he's disgusted with what he's had to do to serve justice. Meanwhile, the comic book Superman mourns the extradimensional innocents that died but doesn't seem to spare a thought for the Kryptonians he's just basically murdered. Furthermore, the MoS Superman only killed in a heat of the moment decision, having been left with the impossible choice between the lives of an innocent family and that of Zod. Meanwhile, comic book Superman planned his execution and could have stopped at any time. Comic book Superman's wasn't a last-minute choice; his was a cold and calculated plan.
It's worth noting that MoS wasn't the first time Zod has been vanquished on film. In 1980's Superman II, Christopher Reeve's Man of Steel tossed the villain into a seemingly bottomless crevice in the Fortress of Solitude during the film's finale. Still, neither this nor the Man of Steel take on Zod's ultimate fate seem to hold a candle to the callousness on display in the comics. Superman may be the perennial good guy hero, but not even his cape is entirely clean.