The Vampire Diaries may be most famous for its angst-ridden love triangle of Elena Gilbert and the Salvatore brothers, but the show had many other memorable characters and some of The CW's most notable villains. One of the best was Katherine Pierce, who may have looked like Elena, but they couldn't be any more different from each other. While other vampires were loud and flamboyant in their actions, Katherine was quick, efficient, and merciless, siring several vampires during the course of her eternal life.
Katerina was over 500 years old, and she spent much of that time escaping Klaus and other enemies. She seldom had companions, but when she took a liking to someone, she tended to turn them into vampires for her convenience. Almost all the Mystic Falls tomb vampires, and a few others, were sired by Katherine.
Pearl Zhu
Katherine was one of TVD's strongest vampires who never turned her humanity off, which was perhaps why she turned Pearl and her daughter Anna into vampires as they struggled with consumption. Katherine sired them at around about the same time she had become a vampire herself since Pearl told Damon she was 400 years old when they skirmished.
As a human, Pearl's husband and children (with the exception of Anna) had succumbed to tuberculosis, and she went to Katherine for a cure. The vampire must have felt some comion for Pearl, which was why she turned her and her daughter. Pearl and Katherine stayed fast friends for centuries after that.
Annabelle Zhu
The only surviving daughter of Pearl Zhu, Annabelle was sired at the same time as her mother. She was extremely sick and saved from her disease by being turned into a vampire. Since then, Anna lived a happy life with Pearl and Katherine until they were both entombed by the Founding Families of Mystic Falls.
Anna was a determined young woman who was loyal to her mother and had spent 145 years trying to free her from the tomb. She tried to take revenge but ended up in a tragically misunderstood TVD romance with Jeremy Gilbert. Even though Katherine was her sire, Anna did not care to locate her while she was out of the tomb, as they were not as close as Katerina was with Pearl.
Stefan Salvatore
Stefan was indisputably Katherine's greatest love, and she found him entirely by chance when she posed as an orphan girl seeking shelter at the Salvatore Boarding House. Her fondness for both brothers interfered in their relationship, but Katerina did not care about any consequences. She wanted him to be a vampire to be with her eternally, even if that meant she had to compel and control him.
Uncompelled, Stefan was not happy about Katherine being a vampire. She manipulated him and fed him her blood, although the killing shot was launched by Giuseppe. However, Katherine very much intended to do the same, just later on. Her motivation here was love and selfishness, as she wanted Stefan all to herself, without bothering to ask him what he wanted.
Damon Salvatore
Of the two brothers, Damon was the one who accepted Katherine as her vampire self and didn't need to be compelled to drink her blood. The best decision Katherine could have made was to leave Stefan alone, and choose Damon as her mate, but she wanted the best of both worlds. Since she couldn't choose between the Salvatores, she sought to turn them both and have them as her eternal playmates.
Damon died next to Stefan, and they both woke up as vampires together. Katherine's blood had turned Damon, but when he awoke, he was on the fence about making the transition. He still loved Katherine for centuries, until she let him down one last time.
Noah
Noah was a minor character in season 1 who was obsessed with Elena because of how similar she looked to Katherine, his sire. Not much is known about Noah, except that he was supposed to be helping Anna free the tomb vampires, but lost interest when he found Elena. He was turned in the 1800s by Katherine, but the reason is unknown.
Noah claimed to have known the Salvatores when they were humans, so he was from Mystic Falls itself. It is believed that there was a young deputy named Noah who worked with the sheriff in 1864 to hunt vampires, and it was this human who was sired by Katherine.
Henry Wattles
Damon's friend and army mate Henry appeared several times in the show, sometimes as a ghost in his memories, and other times as the very real vampire that Katherine turned him into. Henry was among 26 other vampires who were entombed under Mystic Falls, and most of them had been sired by Katherine.
It is not known why Katherine turned Henry, but convenience could very well be the reason. Katherine turned people who were inconvenient to her, or those she liked and wanted around for a while. The exact reason for her siring Henry remains a mystery.