In yesterday's #RurouniKenshin episode, every time Kenshin encounters an adversary he offers to avoid "fuyō no tōsō", unnecessary fights.
For the first word, I found two options in the dictionary:
不要 (not + need): https://jisho.org/word/%E4%B8%8D%E8%A6%81
不用 (not + use):
https://jisho.org/word/%E4%B8%8D%E7%94%A8
Both are pronounced ふよう (fu-yō), but #Japanese has several homophones which are considered distinct words. In writing, you should use the one with the desired meaning.
So in this case, 不要... maybe?