However, the main character should be doing this for his own purposes (tell me if i need to clarify ^^;

So... something along the lines of

Ubel Blatt
Red Eyes

I'd prefer no shoujo/josei but if you think it's good, post it anyways =D

Berserk
Destroy and Revolution
Akumetsu
Death Note
Carnivorous Princess Yegrinna
Zero
Dohran

There should be some that fits in your criteria.... I think...

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Theres Hoshi no Samidare
Well the character doesn't want revenge on the world, but she does want to destroy the earth. I know its not exactly what you are looking for, but it might be close enough.

Gankutsuou, and by world it's more like people who are in the process of getting to rule it.

Your examples are more along the lines of hunting down and killing a very specific group.

Similar titles:
- Knights
- Legend of Basara
- Legend of the Galactic Heroes (more of a space historical war opera but the manga series is largely about vengeance against the existing Imperial structure; alternatively known as "Prussians in Space")
- Ginga Sengoku Gunyuuden Rai (Johji Manabe's space epic; also known as "Samurai (Sengoku) in Space"; also, his h-doujinshis can be considered as canon to the main story, especially once you read the Gaiden)


Non-violent alternatives:
- Skip Beat (highly recommended, the anime is a hilariously perfect adaptation)
- Shinryaku! Ika-musume

This sounds like Count of Monte Cristo (novel) and to a certain extent Erik from Phantom of the Opera (novel, film) also I believe there's a similar manga based on this novel but I can't remember the name

seconding Death Note... oh my such a good manga!

Monster maybe? But my memory kinda fuzzy so I'm not sure about this

Silver (FUJITA Kazuko) is about revenge but it's only towards one guy if this suits your taste, then you can try Yami no Alexandra that deals with revenge as well. She wants a revenge for her father's death

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Help! I'm looking for... manga with dangerous guys http://www.mangaupdates.com/showtopic.php?tid=39874&pa ge=1#post594033

If you don't mind josei one-shots, check out Kayase Shiki's "Kimi to Boku to Sekai no Owari" from Arcana 12 (story 4) and "Hebi no Ou" from Arcana 16 (story 5).

If I were you I would look under the category "emo".

Hmm, I've read Death note, akumetsu, hoshi ni samidare, monster, and reading knights right now.

Well, monster wasn't really revenge against the world, the main antagonist was just evil.

Hoshi ni samidare wasn't really revenge either, she just wanted to not be left behind.

I'll check out the rest, so thanks for the suggestions guys :]

@binturong, emo category?