Leah and Marcus

Marcus was Leah's first serious relationship and she considers it a failure. Despite being sent by Douglas to use Leah, Marcus did genuinely care about her, to a degree. His betrayal is what caused her to give upon love and deny her feelings for Chase. After he was recreated, Leah was shocked and tried reason with him. Marcus chose to get revenge on Douglas over his love for her, This was when Leah realized he was beyond redemption, and after he tried killing Daniel, made Leah hate him all the more.