My two most hated book love interests:
Derek Hawke from Jennifer's Wilde's Marietta Trilogy. Even by bodice ripper standards he is such a cold and abusive piece of shit. Thankfully the author is fully aware of how horrible he is and the heroine eventually leaves him for someone else.
Travis Maddox from Beautiful Disaster. I can tolerate troubled bad boy characters in fiction if they're compelling, but Travis is just a violent and misogynistic loser. Actually the whole book is such a misogynistic trainwreck that I was left wondering if the author had a single female friend in real life. Seriously, 99% of the girls in the book are referred to as skank bitches, sluts or STD-ridden imbeciles by our delightful hero. The heroine is of course Not Like Those Other Skanks because she's pure and virginal and therefore worthy of Travis. The only good thing about this awful book and romance is the 1 star reviews on Goodreads (which were more entertaining than the actual story.)