Masamune-kun no revenge. A story about a boy who, after being heartbroken invests his following 8 years into reshaping himself into every girls wet dream, and then proceeds to serve the cruel girl her own medicine, making her fall for him, then leaving her heartbroken. The story ends with the boy realizing the vanity and emptiness of revenge, and going out with the girl seriously.
EXCEPT it doesn't.
This manga starts out interesting, with a decisive, determined MC, and actually cruel rich girl. MC sacrifices his chances for friendships, relationships and fulfilled love only to achieve his revenge, slowly learning of the pain and hardship the said girl is actually going through.
And then, at the ending, it's all just denied.
YEAH, JUST LIKE THAT. All his effort is DENIED,the whole story becomes worthless! He could remain that fat kid that bought acquitances with his dad's money and the hot girl would go out with his regardless, BECAUSE IT TURNS OUT SHE'S COMPLETELY INNOCENT and loved him all along, and the one that broke his heart was actually not that girl, but someone else that IMPERSONATED that girl and dumped him out of spite.
Seriously, that ending is just such a filthy, obscene pile of deus ex machina shit I regret reading this far.



TL;DR/ SKIPPING THE RANT/ THE MOST IMPORTANT PART:
It's a fun manga. That ends at chapter 36. Anything beyond that point that's not a filler is a shameless changing of the main plot to an insult to anyone who faithfully read previous chapters. So don't.

In one sentence, this manga proves you can ruin whole manga with one single chapter.