Unreasonable
Irrational
noun, な adjective
Reason is not exhausted... but what you're asking is unreasonable. Soon my reason will be exhausted, though.
りふじん
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
超理不尽な上司とやっていかなくちゃいけなくて、理想の仕事が一気に悪夢になったよ。
My dream job turned into a nightmare all at once because I had to deal with such an unreasonable boss.