It's hard to find a supernatural creature who didn't love Katherine Pierce at some point, and even harder to find one that she actually loved back. Katherine was never short on suitors in The Vampire Diaries, but she struggled to form meaningful connections because of her tendency to choose self-preservation over everything and everyone.
Katherine's willingness to sacrifice the people she cared about to ensure her own survival turned plenty of her former lovers into enemies. She betrayed countless vampires, werewolves, and witches throughout her five hundred years on Earth, making her death a celebratory event for most of the main characters in the show. However, there was a man or two that Katherine claimed to genuinely love, and viewers experience a more selfless side of her when they were around.
Klaus Mikaelson
Klaus might be Caroline's best match, but there's no doubt that he's at the bottom of Katherine's list. It's easy to forget the two had a romance because of how much they hate each other, but Katherine and Klaus weren't always enemies. Klaus was smitten with Katherine until he realized that she was the Petrova doppelgänger.
It's rare for Klaus to love someone more than himself, and Katherine did not fit into that category. She turns herself into a vampire to prevent him from breaking the curse, and he slaughters her entire family out of revenge. Out of all the centuries Katherine was around, it remained the worst day of her life.
Trevor
Viewers only got brief glimpses of Trevor, but he played a crucial role in Katherine's life. Everything he did was because of his love for her, and Katherine is the reason he and Rose spent 500 years on the run from the Originals.
Trevor wasn't a bad person, and he put his life on the line for the woman he loved. But as Rose tried to tell him, Katherine never had any real feelings for Trevor and was using him as a means to stay alive. Because of how unequal their relationship was, Katherine probably didn't think twice about Trevor after she got what she needed from him.
Mason Lockwood
It came as a shock when The Vampire Diaries revealed that Katherine and Mason were an item. Mason arrived in Mystic Falls after the death of his brother, but it was clear that he had ulterior motives for being there. Werewolves and vampires hooking up was a rarity, and it added to the already surprising twist.
Mason was convinced that Katherine truly did love him, despite Damon insisting that he was being used. Sadly, Damon was right, and Katherine seems only slightly annoyed when she finds out that he's been murdered. But Mason's feelings for Katherine were real, and he would have likely done anything she asked him to do.
Damon Salvatore
If Katherine would have only loved him back, Damon would be a contender for the top spot. He's loyal to the people he cares about, and he's proven with Elena that he would walk through fire for the woman he loves. That was Katherine at one point, and Damon spent over a century trying to find a way to save her.
He figured out early on that Katherine didn't die in the fire in 1864, and that the vampires had been sealed in a tomb beneath the church ever since. Everything Damon does in the first half of Season 1 is to get Katherine back, but Katherine was never there. She had been alive the entire time and never came to see him. Damon took it hard, understandably, when he found out the woman he had dedicated his life to didn't even care enough to visit him.
Elijah Mikaelson
Katherine didn't love many people, but a case could be made for Elijah. Katherine claimed to be in love with him, but she says a lot of things that she doesn't mean. However, actions speak louder than words, and Katherine gave up her freedom from Klaus to prove to Elijah that she cares for him.
Surprisingly, there was no ulterior motive. Elijah is one of the few characters who gave Katherine another chance, and it wasn't something she took lightly. Elijah is the most moral member of the Mikaelson family, and that's what Katherine is drawn to. It's especially ironic because Katherine has almost no morals, herself.
Stefan Salvatore
Stefan Salvatore is objectively Katherine's best love interest in the series. He was the only person that she loved unconditionally, and it was Stefan that made viewers see Katherine as less of a villain and more of an anti-hero. As the show continued, there were several flashbacks that shed light on their relationship and proved that Katherine loved Stefan ever since she met him in 1864.
She promised Stefan that they would be together again, and checked up on him throughout the decades, even if he wasn't aware of it. Katherine has risked her life for him on several occasions, despite always putting herself over others. Stefan did genuinely love Katherine at one point, and when she came back into his life, he believed she was capable of redemption. If Katherine hadn't snatched Elena's body before she died, things could have gone very differently for the pairing.