For me, Katniss Everdeen is a hit-and-miss character. I loved her in The Hunger Games, but I liked her less and less as the series progressed. Why? It's simple: she went from a proactive character to a reactive character. Let's explore the difference.
In The Hunger Games, Katniss is established as a proactive character from the beginning. When her father dies, Katniss's mom is so overcome with grief that she can not provide for the family. So Katniss takes it upon herself to do so. She learns to hunt, she learns how to make a living for the family, and she even takes over as a mother-figure to her younger sister.
You might argue that she is only reacting to her father's death, but the difference between Katniss and her mom is clear. The mother only reacts, but for Katniss the tragic event is a stepping stone to becoming an expert huntsman and survivor.
Similarly, when her younger sister Primrose is picked for the Hunger Games, Katniss takes matters into her own hands by volunteering to go in Prim's place. She won't let bad luck define their fates; instead, she decides to face the challenge. As she heads into the Games, she has a strong incentive to survive at any cost because she wants to return home and continue to care for her family. But even in the Games, she never lets her goal overcome her humanity. The scene with the berries at the end is Katniss's ultimate moment of not accepting her fate.
Such a great heroine! And yet, let's look at Katniss from Mockingjay. In my view, our strong heroine turns into a reactive fatalist. Not only does she spend most of the book moping about what happened to Peeta, she never really takes action in the rebellion that she started.
Of course, she is slowly realizing that the new regime might be just as corrupt as the previous one. But what does she do about it? For the most part, she continues to follow their directions, going on the missions they assign to her, giving into the photo shoots, and hiding in closets. It's not until the very end that she reacts to the regime with a single act of violence against a leader. For me, that one moment did not have enough impact because Katniss was never driving the story, never fighting for change even as opportunities came her way. Why didn't she start her own rebellion if she felt the current one was misled? She had turned into a fatalist, convinced there was nothing she could do to improve the world.
Her fatalism is best symbolized by her choice between Peeta and Gale: she never really chooses. When one of the guys does something she can't forgive, she ends up with the other one because...well, essentially because he is still around.
It seemed that Collins was more interested in portraying a boot to your face, 1984 type world than she was in creating a strong heroine. As the author, obviously she is the one to define the meaning of the story, not me. But, personally, I had expected a proactive character, a strong heroine to take center stage. Mockingjay left me thinking What happened to the kick-butt survivor Katniss?