aang having a code against killing makes sense because as the last airbender he carries the weight of his entire peoples and culture on his wee shoulders, and that includes respecting and valuing all life. it is core to his being, and him finding a roundabout way to solve the issue of killing ozai makes sense both as an airbender and for the story. we find out later in the kyoshi series that murder literally inhibits your ability to airbend, hence kyoshi and her mother's use of fans! and dont bring your utilitarian "oh we can save more lives by killing one person" into this, because sure that can work for another show but not this one!! it is literally the core thesis of the show! have some media literacy my god