It's not seen as love, first of all, but I'd like to inform whoever asked this question as well as a large portion of the fandom that Levi did not rape Lacie. That is a huge misconception. Levi told Lacie about the experiment he wanted to perform involving someone having a child in the Abyss, and she agreed to it. He did not impregnate her against her will. On a separate note, Levi never abused Lacie at all.