Gar Logan / Beast Boy

Earth-One / Post-Crisis / New Earth
Gar met Tara Markov / Terra on top of the Statue of Liberty, which she was trying to destroy. A confused and troubled runaway, Terra (Tara Markov) was persuaded to seek sanctuary at Titans Tower (New Teen Titans, vol. 1, #28,1983). Terra even joined the group as a full-fledged Titan (#30) Terra was revealed as a spy for Deathstroke the Terminator. Seeking to fulfill his contract with the H.I.V.E., Deathstroke enlisted Terra’s aid to infiltrate the group and learn their secrets. As part of this ruse, Terra especially manipulated Changeling, who had developed a crush on the cute blond geomorph.(#34, 1984) A tarted-up Tara was shown plotting the Titans’ demise while enjoying a post-coital smoke with Deathstroke. And after a brutal training excercize with Slade, Terra denounced “cute girl super-heroes” and vowed to kill all the “sanctimonious do-gooders.” Over the next several issues, she showed signs of being swayed to the Titan's side. She and Gar even shared a kiss (Tales of the Teen Titans #42)

Once revealed as a traitor, a heartbroken Changeling suspected hypnosis. But Terra confessed, “What’s with the dropped mouth, Logan? Your pwetty widdle girlfriend isn’t all true-blue and pure? Mister, you don’t know the half of it. But you better believe you’re gonna squirm while I tell you everything.” (ToTT Annual #3).

Nightwing and Jericho liberated the Titans, while the H.I.V.E. Fell in ruins. Changeling reached out to Terra one last time, causing the mudslinger to lash out, “It’s all been an act. Every part of it — ‘specially that kiss, Logan. That was the biggest act of all. It made me want to gag kissin’ you, Logan.” Ultimately, Terra’s own rage consumed her and she buried herself in a mountain of debris, her body being found by Gar.
 * 1)  Raven  and Gar fell in love while Titans. As far as I know, their relationship continued up to Flashpoint.

New 52

 * 1)  Tara Markov / Terra  - In this version, Tara is a heroine and she and Beast Boy have a much mroe placid relationship, falling for each other and becoming a couple.