Caroline and Liam

This is the relationship between the vampire Caroline Forbes and the human Liam Davis. Initially, Elena tried to set up Liam with Caroline in Welcome to Paradise, however Liam seemed to be interested in Elena. Liam and Caroline officially interacted at Thanksgiving in Fade Into You. After turning her humanity off, Caroline went to a bar where she hooked up with Liam and later on fed on him. She also compelled him to do several of her tasks, including performing surgery on Stefan's niece, Sarah Nelson, to force Stefan to turn his humanity off.

Season Six
In Welcome to Paradise, Elena planned to set Liam up with Caroline. However, Liam showed more interest in Elena.

In Fade Into You, Jo was telling Caroline, Elena, Tyler, Liv, and Luke, about her past and about Kai. Unaware to them, Liam was still in the room. Caroline quickly compelled Liam to go upstairs and get wine to let Jo finish her story.

In The Downward Spiral, Caroline is at a bar where Liam suddenly approaches her. She comments that he is much cuter in person. Caroline drunkenly tells him that her mother recently died. He seems concerns about her behavior. However, she brightens up and they are later seen making out passionately. Suddenly Caroline reveals her vampire face and bites him and feeds on him, while he screams in horror.

Caroline soon returns to her dorm and tells Elena how she ran into Liam at the bar. Elena asks Caroline what she did to Liam, to which Caroline replies that she "ate him." Caroline tells her that the voice inside her head that tells her to stop feeding didn't say anything. She then promises to keep her behavior under control if allowed to have her humanity off for one year. She warns Elena and Bonnie that if anyone wants to turn her humanity back on that she will become their worst nightmare.

Liam later goes to attend Caroline's huge rave party. She runs into Liam at the party and asks him if he's good at surgery. Liam replies that he's terrible at it since he's only a sophomore in college. Caroline smiles and precedes with her plan.

Caroline compels Liam to perform surgery on Stefan's niece, Sarah, as an act of revenge for trying to get her to turn her humanity back on.