Here is the context including the word.
なにが なんでも たたきのめさにゃ 気のすまぬ 男が俺の眼のまえに立ちはだかったんだ。
I found a word 「気がすまない」 in an online dictionary which gives the meaning of it as 'not to be able to settle down (if something is not done)'. I'm not sure that particle 「の」 in the word would make its meaning differs from the one using particle 「が」 instead.
If their meanings are similar, could I translate the whole context like the following sentence?
There was a guy who blocked my way that I must desperately to beat him down, whatever it takes.