I want to read something where the main character is in love with someone who ends up betraying them. Doesnt matter how. But I want that very same person who hurt the main character to come crawling back only to get completely rejected. Then I want the main character with someone else.

Dont recommend Skip Beat. Its not or even close to finished, its very long, and you have no idea how it will turn out. For all you know it could have a Hana Yori Dango twist.

No wishy washy main characters who consider taking them back. As realistic as that might be the idea of that makes me feel physically ill.

I cant think of any examples tbh.

Uwasa no Midori-kun!! might fit all of that. (The only thing I'm not certain of is the "complete" rejection. It's not completely scanlated, but there's a thread about what happens in the end, so I know that much.)

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If you've ever thought or said "Nice Guys finish last" and really meant it, then you should probably read this LJ post by DivaLion. It's incredibly insightful whether you're male or female.

From a bumper sticker I like:
"If you're gonna ride my ass, at least pull my hair."

Sheet no Sukima the one-shot which has this title would fit

and you could also try Kanojotachi no X-Day it isn't about betraying but the situation is somehow similar