が必要 => need; necessary N4
必要がある => Need/Need to N4
[必要「ひつよう」]はない => It is not necessary for A to be done N2
Needs, Requirements
... 反対に => on the contrary N3
Compare
に対して => towards; against; regarding; in contrast with ~​ N3
のに対して => towards; against; regarding; in contrast with ~ N2
必ずしも~とは限らない => Not necessarily; not always N3
…と (は) はんたい (反対)に => opposition; resistance; antagonism; objection; dissent N3
Compare
[要「よう」]するに => A. In short/put simply, B N2
Adjectival, Descriptions
要するに => in short; in a word; to sum up; to put it simply ~ N2
に[対「たい」]して/に[対「たい」]しては => In response to (topic) A, in regards to A, considering A, in contrast to A N3
Reason, Result, Response
に[対「たい」]して/に[対「たい」]しては => In response to (topic) A, in regards to A, considering A, in contrast to A N2
Reason, Result, Response