I'll keep this short and spoiler free: you need to read this manhwa. TL;DR at bottom
Story: Very interesting premise that stays captivating from start to finish. A lot of manhwas feel like a train on fire during their second half - not only is [Kill the Villainess] interesting at the start, I'd say it gets even more intense towards the end. I do have to warn you though - don't expect this story to be all rainbows and butterflies. It's a rather grim and heart wrenching read for the most past. I guarantee though that you'll love the ending.
Characters: The characters are well written, with a lot of them being nuanced. Most of them have huge daddy issues and past traumas, but man they're complex, and the villains are especially revolting - I love how the author portrayed all the usual toxic ML clichés in novels. I especially adore the "love rival", and the female lead, and how unlike your usual protagonists, she actually misses her family/home. And the male lead? Gyatt dayum, this guy is the ultimate green flag. It's rare to find a husbando as good as him when manhwas are filled with toxic douches.
Art: The art is gorgeous. Any scene with the female lead could be used as a phone wallpaper, and the most important part - it stays consistent from start to finish without decaying towards the ending.
Why should you value my opinion? I've read dozens if not hundreds of manhwas, from romances, to reincarnation/transmigration tropes, to villainess tropes and a lot of them suffer from a bad case of diarrhea second half/ending, leaving you with a shitty aftertaste in your mouth. [Kill the Villainess] is worth it, it's a breath of fresh air and will leave you satisfied at the end.
TL;DR Read it! It's a dark and quite heart wrenching story, with great complex characters (some of them rather disgusting), great art and super entertaining that will keep you on the edge of your seat from start to finish!