Need help for Japanese Romaji

Greetings Dopers.

I’m working on a project involving a fictional Japanese swordsmanship style, but my Romaji is spotty, at best. Basically, its a two-sword style that progressively gets more powerful the more a practitioner strikes. Since this will be used for a “villain” character, I’m thinking of something sufficiently over the top and violent, like say “relentless murderer two heavens as one” or something like it (“two heavens as one” being lifted from the real-world style “Niten Ichi-ryū” of Miyamoto Musashi).

Also, a technique for this style will be something called “Five-hit instant death”, which I think translates to “Gogeki hissatsu”, though I’m not too sure.

Can anyone help this guy out?