Final answer:
Sevro, a character in the Red Rising series, is known to have killed his enemy. He's a complex character with actions deeply explored within the context of the series.
Step-by-step explanation:
The character Sevro from the Red Rising series by Pierce Brown is known for a number of violent and decisive actions. Responding to the question 'Who did Sevro kill?', the correct answer is: d) His enemy. Throughout the series, Sevro, a member of the Howlers and a close friend of the protagonist, Darrow, is involved in many battles and conflicts. His actions, though sometimes brutal, are often directed towards his enemies in the context of the rebellion against the oppressive Society. It is important to note that Sevro is a complex character, and the moral implications of his actions are extensively explored in the series.