You know, Sakura is not that hated generally speaking. It's just that alot of Sakura haters have somehow ended up on this site.
1. She had more devlopment then any K11 except Sasuke and Naruto *Two Main Characters*
2. She is a main character, but as you can Kishi is focused on Naruto-Sasuke more then on anything else. He is generally terrible at creating a strong, heroine like female character, considering that there is not a single one in Naruto-verse.
3.Part 1 and Fillers dont count. You can count on fingers how many times she hit him in Part 2. Just because you watch fillers where everyone's personality and skills are totally different, does not mean that is how Kishi meant to show her. And her hitting Naruto is supposed to be comical, not a way to harm him. Remember, in Japan they see things differently.
4. War arc is not over, and it has been foreshadowed for some time now that Sakura will get her development. Most recent one being Heroes, Heroins make your moves or something along those lines. Since then we have seen Narutos big moment, Sasukes big moment, and I predict we are going to see Sakuras soon. If you want more information read Chattes (Or whatever her new name is) Thread.
5.First of all, she wanted to do it for Naruto, because she obviously cares for him, but killing your teammate, someone you loved for quite a while ain't as easy as you think. Naruto wouldn't be able to do it. It took Kakashi whole part 2 to decide he would do it. Hiruzen was not able to do it to Orochimaru. Hashi wasn't able to do it to Madara. Stop making useless arguments like that. If she was a villain and was not able to do it, I could see how that could make her a bad villain, but as a "heroine" its good that she does not have a cold hearth, and is not able to kill so easily.