Oh, you know the type: they collude, sneak, back-stab, start rumors, slander your character, dishonest about intentions/deceptive, manipulative, and just plain snake-like (figuratively and literally).
If they get found-out, they will do damage control: sickly sweet, over accommodating, constant check-ins, and anything else that will smooth it over with you.
They're really not concerned about making amends due to feelings of conviction, but rather to "appear" in a good light. It typically lasts for a small while, then you catch them again doing their sneaky serpentine behaviors. They don't really care for you, you are just someone to use to satisfy their desires and goals.
These types often present themselves as overly nice, incredibly sweet/charming, and endearing. When you call them out be prepared for some of the most vile things you've ever heard directed at you and about you. Sometimes, in dealing with these types, you must consider that they simply have no conscience. I believe through living and extensive research, that some are born without a conscience, and some have been so horribly brutalized that their psyche snaps/breaks (ability to feel convicted is covered by a jagged, hard shell).
While we're to love even our enemies, we must be careful to only surround ourselves with people that don't take advantage of us. Whether it be family, friends or coworkers, a "user" must be put at an arm's distance with healthy boundaries.
Has someone in your life that uses you AND talks shit about you, and all the while smiles and acts as if nothing has happened? You may consider that they are simply performing damage control.