事前に必要[jizennihitsuyou] prerequisite
生者必滅[shoujahitsumetsu] All living things must die
絶対必要[zettaihitsuyou] absolutely necessary
必ず[kanarazu] always
必ずしも[kanarazushimo] (not) always

必ずや[kanarazuya] certainly
必携[hikkei] handbook
必見[hikken] worth seeing
必殺[hissatsu] certain kill
必死に[hisshini] frantically

ブチ殺す[buchikorosu] to kill by hitting
押殺す[oshikorosu] to crush to death
あっ殺[assatsu] crushing to death
暗殺[ansatsu] assassination
暗殺事件[ansatsujiken] assassination

一殺那[issetsuna] (a) moment
殴り殺す[nagurikorosu] to strike dead
殴殺[ousatsu] beating to death
皆殺し[minagoroshi] massacre
かみ殺す[kamikorosu] to stifle a smile, yawn, etc.