Man, vampire romance is so oversaturated now, it's hard to sift through. You need something that doesn't feel like it was churned out in a week. The ones that stuck with me had a real sense of consequence—the love actually felt dangerous, not just in a 'bad boy with fangs' way. 'The Beautiful Quartet' by Renée Ahdieh does this gorgeous, atmospheric thing set in 19th-century New Orleans. The tension is more of a slow, simmering poison than a sudden explosion, which I loved.
For a completely different, much darker flavor, J.R. Ward's 'Black Dagger Brotherhood' series is a commitment, but the earlier books, especially 'Dark Lover', have this raw, gritty intensity. The world feels lived-in and brutal. I burned out after book six or seven, though—it starts to get repetitive. A weirdly effective standalone is 'Empire of the Vampire' by Jay Kristoff. It's more grimdark fantasy, but the central, tragic romance embedded in it absolutely wrecked me. It's less about yearning and more about grief-laced devotion.
I'd actually steer clear of anything labeled 'romantasy' if you want intensity. That label seems to promise heat but often delivers a very formulaic, frictionless kind of passion. The intensity comes from the stakes feeling real, not just from how often the characters rip each other's clothes off.