The Hunger Games
End of Book
I would say the main antagonist of the book is the Capitol and the government that runs Panem. The goal of the Capitol in creating the Hunger Games is to remind the people who live in the 12 districts that they have the power and can destroy them just like they did to District 13. They want to supress the people with fear. The end does justify the means to the Capitol, because they will stop at nothing to get what they want. They don't care that their people are starving, and they will kill people for entertainment. Keeping the districts in line does satisfy the Capitol.