This is not distinguishing between people who cannot kill the soul and people who can kill the soul. No person can kill the soul. Alternate translation: "Do not be afraid of people. They can kill the body, but they cannot kill the soul" (See: [[rc://en/ta/man/translate/figs-distinguish]])
You can add "because" to clarify why people should fear God. Alternate translation: "fear God because he is able" (See: [[rc://en/ta/man/translate/writing-connectingwords]])