Job's comforter

One who is discouraging or saddening while seemingly offering sympathy or comfort.

[After JOB¹, whose friends pretended to comfort but actually found fault with him.]

Three friends of Job who visited him in his affliction and offered him a way of making sense of his troubles: namely, that he was getting what he deserved. Job's friends maintained that misfortunes were sent by God as punishments for sin, and thus despite Job's apparent goodness, he must really be a terrible sinner. Job persistently disputed them, saying that God is supreme and mysterious — that God can send misfortunes to both good and wicked people and may not be second-guessed.

The noun has one meaning:

Meaning #1: someone whose comfort is actually discouraging