YOU SAID:
Why must I kill you??
INTO JAPANESE
なぜあなたを殺さなければならないのですか?
BACK INTO ENGLISH
Why do I have to kill you?
INTO JAPANESE
なぜ私はあなたを殺さなければならないのですか?
BACK INTO ENGLISH
Why should I kill you?
INTO JAPANESE
なぜ私はあなたを殺すべきですか?
BACK INTO ENGLISH
Why should I kill you?
That didn't even make that much sense in English.