Even though it was a vampire show, The Vampire Diaries put a lot of emphasis on romantic relationships as well. The most prominent romances were those between the show's three main characters, Elena Gilbert and the Salvatore brothers, Stefan and Damon. However, most of the other characters found the time to find their perfect or not-so-perfect partner in some cases.
Both Katherine and Klaus were mostly single during the show as they focused on their evil plans instead. Some fans then wondered what would happen if these two got together and whether Katherine and Klaus could work as a couple in the first place.
Perfect Together: They Always Had A Plan
Katherine and Klaus have many things in common but one that connects them closely is that they're determined to survive. As a result, they always have a plan, and when that plan fails, they come up with several more.
Katherine spent 500 years running from Klaus and Klaus spent 1000 years running from Mikael - both of these things required a lot of maneuvering from Klaus and Katherine, so together, they'd be unstoppable.
Never Work: Klaus Is The Original Vampire
Unlike other vampires, Klaus is one of the oldest ones, The Originals as the spinoff was called. Vampires get stronger as they get older, but the Originals have an extra perk - they're much harder to kill.
Katherine, on the other hand, is a normal type of vampire, which means that she'll always be the more vulnerable one in her relationship with Klaus, which wouldn't be something she'd like.
Perfect Together: They Were Similar As Humans
In the present day of the series, it's somewhat difficult to picture it but both Klaus and Katherine were the good guys once. Klaus loved his family and was gentle and kind but he feared his father. Katherine was very similar to him, possibly less naive, but still a good person at heart.
Life hasn't been kind to them, and as a result, they became darker people when they turned into vampires, but once upon a time, they had more in common than either of them would have liked to acknowledge.
Never Work: Their Friends And Families Would Be Against It
It might not look like such a big deal but family and friends disapproving of one's choice of a romantic partner can make the relationship sour. Elijah liked Katherine himself, and if Katherine got together with Klaus, he wouldn't take it well.
As for Katherine's side, the Salvatore Brothers and others would probably try to break the reunion since they would believe Katherine and Klaus ing sides would be too dangerous for them.
Perfect Together: They Like To Manipulate People
It doesn't make either Katherine or Klaus very sympathetic, but shared bad virtues can bring people together. Both Katherine and Klaus enjoy manipulating people, making them do their bidding.
At first, Katherine toyed with the Salvatore brothers and Klaus later did the same, not to mention him wreaking havoc on the lives of multiple Mystic Falls citizens.
Never Work: They Only Think Of Themselves
A relationship between two people is often based on a strong mutual connection between them. The problem is that Klaus and Katherine mostly think only about themselves and their benefit. Klaus cares about his siblings but he punishes them every time he feels they step out of line.
And Katherine uses even the people she likes to fit her goals. Neither of them would be truly emotionally invested in the relationship, so it wouldn't work in the long run.
Perfect Together: They're ionate People
Even though Klaus and Katherine wouldn't most likely last for a long time, they could have a brief relationship, more based on physical attraction, shared ambitions, and goals than actual love.
Katherine and Klaus are ionate people by nature, and when they love, they love fiercely and quickly. Klaus has had multiple relationships throughout the centuries, and he usually pursued them with ion. The same is also true for Katherine.
Never Work: Klaus Wanted To Sacrifice Katherine
Of course, the biggest problem between this couple would be that Klaus wanted to kill Katherine for centuries. When Elijah introduced Katherine to Klaus in the 1490s, Klaus planned to sacrifice Katherine in the ritual needed for him to become a hybrid.
When Katherine learned of this plan, she became a vampire and ran from Klaus. He never forgave her for that and planned how he would torture her for centuries. Klaus isn't big on forgiveness, and he would have a hard time getting over his grudge.
Perfect Together: Before She Died, Katherine Liked Him
However, before Katherine did learn about Klaus's evil plan to sacrifice her, it looked like she was in love with him, or at least liked him strongly and found him attractive. Katherine thought Klaus was genuinely interested in her, and it seemed she didn't object to his affection.
From the flashback scene, it's clear that Katherine likes what she sees when she meets Klaus for the first time, and she doesn't mind it when he starts to court her.
Never Work: Klaus Killed Her Family
Unfortunately, any chance at a relationship between Klaus and Katherine died the moment when Katherine discovered Klaus murdered her family. Katherine had very few people she was close to but she loved her family, especially her mother.
She was devastated when she found them dead and realized that Klaus took his revenge on her in this way. She never would have forgiven him for that, no matter how much time would have ed in between.