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

他是一个性格复杂人——喜怒无常,反复多变,忧郁寡欢.

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

他变得喜怒无常、不可理，鸡毛蒜皮小事就殴琳。