There are some characters that can never be forgiven, especially for what they do to the one person they're supposed to love.
Fair warning, there will be mild/moderate spoilers here as I discuss why these people are bad love interests.
Counting down these are the worst love interests I could think of:
5. Aspen Leger, The Selection series
Having only read The Selection so far, I'm basing my opinion of Aspen on that alone. He's a two faced jerk who loves America, but then rejects her because he's a lower caste number than her and doesn't want to drag her down with him. She tries to move on when she's Selected, but then he becomes a guard and professes to still love her and asks her how she can possibly stand the charade of the Selection. Seriously, dude, knock it off and move on.
4. Katniss Everdeen, The Hunger Games series
There's a lot of intense emotion going on in this book, so some of Katniss's action may be forgiven due to her age and the insanity of what she endures, but I've never seen her as a good love interest for Peeta. Peeta himself is not my favorite character, but he deserves better than to be led on and lied to.
3. Edward Cullen/Jacob Black, Twilight series
As much as I might enjoy these books, neither Edward nor Jacob are particularly good love interests for Bella. Both are incredibly selfish and manipulative, not to mention jealous of each other. It really starts in earnest here in New Moon and continues through the end of Breaking Dawn.
2. Frankie Malone, Tomorrow Will Be Better
Frankie Malone could have easily been a good person, but he deceived Margie (his wife) when he married her. He never wanted to be married, he just wanted to do what he perceived to be "normal". This was cruel because he could never give Margie what she wanted or needed from a marriage and he wasn't truthful about that at any point.
The second prince starts out seeming great. He's a sympathetic character, he shows what we think to be genuine affection for Mare (the main character), only to find out that's he's a traitorous asshole that's been using her all along to further his quest to become king.
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