Well Peeta can throw 100 pound bag of flour over his head.
She has no idea the effect she can have.
Katniss is selfless because she volunteered as tribute to save her sister Prim from entering the Hunger Games, but she is also putting her life on the line.
Katniss is fierce and she shows that she won't be pushed around by anyone. She shows this by shooting an arrow through an apple that is in the pigs mouth by the gamemakers table.
She lacks confidence in herself and feels that she will die right away even when Peeta compliments her she denies it.
Katniss is very determined, after her father died and her mother is in no state to help her family, she has provided for her family for years. Often doing illegal things to get basic necessities like leaving her district through a fence and using a bow and arrow to hunt game which is also illegal. She also trades on the Hobb which is a black market in District 12.
Katniss is a heroine because she is extremely brave, she saved Prim from going into the Hunger Games by going in herself. Entering the Games by choice and putting your life on the line is very brave and is being a heroine to her sister.
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Katniss is a resourceful person, she provided for her family for years on her own, she can craft weapons like bow and arrows, great at knowing which plants are edible and know how to set traps.