cheststabber 

A cheststabber is the polar opposite of a backstabber: That is, they'll tell you straight up that they dislike you. These people deserve more respect than a backstabber does. The cheststabber is remarkably better than the backstabber because cheststabbers have the courage to badmouth you straight up, unlike backstabbers who seem to be absolute cowards because they act like your friend, then go badmouthing you without you even knowing.

Dan: Far out, I hate that guy Ryan! Bloody goes calling me an asshole as soon as he laid eyes on me!
Me: This guy sounds like a cheststabber. I respect him, as I respect all cheststabbers. He had the balls to say what he thinks about you, he didn't back down.

cheststabber by ArchTitans July 2, 2018

chatstabber 

an internet user that pretends to get along with others on the internet in purpose to gain information and use it against them later.

Kim was in a chat room yesterday telling all of Gina's business.
But I thought Kim and Gina were friends?
Guess Kim's a chatstabber.

chatstabber by Jaye November 8, 2004