Y'all better prepare yourself for my villain brainrot cuz I'm still deeply ruminating on Valmont x Riya.
It's not even just me wanting Valmont to be all "I'm a horrible person but I will move mountains for Riya", nor Riya bringing out a lighter side of the grumpy money-fiend, but the dynamics the two would have with the rest of the Dark Hand. Finn, Ratso and Chow would have a roaring good time poking fun at Valmont for his obvious crush on Riya. And when they're actually a couple and being evilly wholesome, Shendu is just there getting tired of their villain sappiness.
M.E.R.V. + Demona would also get in on the fun. Mok would gleefully officiate Valmont and Riya's wedding and be as supportive as an evil rockstar can be of a relationship involving a crime boss and a narcissistic actress who can sing or SCREEEEEEEAAAAAAAAAAM (this only makes sense to people who've watched Rock and Rule). Emma and Demona wouldn't be as loudly supportive as Mok is but they'd sit back and quietly smile while they make out.
Before you ask by the way, no, I haven't been considering adding Zeena and/or the rest of the Deadly Six to this whole affair, cuz a lot of how I see them involves them getting a redemption arc down the line with Zeena even being the outright nicest of them. Wouldn't really fit in with the misanthropic Demona or Emma. (Now the Babylon Rogues...THEY'RE M.E.R.V. material.)