Caroline Forbes has one good romance on this list, Alaric Saltzman two. The relationship they shared was not one of them.
Season 6 introduced viewers and most of the characters to the Gemini Coven. It got its name because, in each generation, a pair of twins born to the coven must fight
to the finish. The winner of “the Merge” becomes a double-strength witch and the coven leader. Alaric’s lover Jo had been born a Gemini but walked away rather than battle (and probably lose to) her evil twin Kai. By the end of season 6, she was pregnant with a new set of twins.
On Alaric and Jo’s wedding day, Kai attacked and eliminated her, destroyed the other Gemini and became a witch-vampire hybrid like the Heretics. Damon ended him, but that couldn’t save Alaric’s twins. Oh, wait, Caroline has a womb — let’s magically put them inside her!
By season 7, which is set three years later (with flashbacks mixed in), she’s gone from being surrogate mom to the twins to being in a relationship with Alaric. He loves her, while she cares about him but still loves Stefan. But she has kids, and he's their daddy, so what the heck, let's do it!
The show didn't pretend Caroline/Alaric were a great couple. It still didn't work.