喜怒无常的

He is a complicated man ——moody, mercurical, with a melancholy streek.

是一个性格复杂人——喜怒无常,反复多变,忧郁.

He became moody and unreasonable, flailing out at Katherine at the slightest excuse.

变得喜怒无常、不可理喻，为点鸡毛蒜皮小事就殴打凯瑟琳。