查个水落石出这话英语怎么说?

查个水落石出 = get to the bottom of a matter
= investigate something thoroughly

广东话人渣 这话英语怎么说？

人渣 = a scum of a community(意译)
= a black sheep(意译)
= one of the dregs of society(意译)

= dregs of men(直译)