The romance genre is full of tropes that create the kind of internal conflict dark romance readers love: one that forces the main characters to really wrestle with themselves before they finally give in to love.
But few tropes do it better than revenge.
This one is up there with the angstiest of tropes, which makes it perfect for dark romance, a sub-genre where the more angst, the better.
With revenge romance, at least one, if not all, main characters are myopic about their need for revenge, unwilling to let it go. Until love gets in the way.
There are multiple ways to spin this trope, which is part of what makes it so fun.
There's the OG, the original gold: one main character using the other to get revenge on a wrongdoer, or, in the case of Nina G. Jones's Debt, a group of wrongdoers.
There's also revenge on the world, seen in the chart-topping Twisted Love by Ana Huang.
And the evergreen—revenge on an ex, like in 12 Days of Revenge by Brittany Wright and Miranda May.
Once you've decided how you want to use the trope, the next step is to determine the motivation behind revenge. Make sure your character has a strong motive for seeking retribution for wrongdoing. The reason needs to be concrete, layered, and above all, emotional. Even showing the character talking about their motivation should result in a physical reaction—think curled fists, a tight jaw, steely eyes, and short breaths.
Create a motive with all three, and you're on your way to sweet, sweet revenge.