Someone who is audacious takes risks in order to achieve something.
①He described the plan as ambitious and audacious.
②Your plan of going abroad is an audacious decision.
③The more audacious and daring the better.
An intrepid person acts in a brave way.
①Some intrepid individuals were still prepared to make the journey.
②The intrepid explorers reached the South Pole.
①Seed your tears deep in your heart it will grow up to valorous flowers.
②Throughout the coming years, he would commit great and valorous deeds.
A dauntless person is brave and confident and not easily frightened.
①Dauntless in spirit,they became steeled through hardship.
②They had audacious ideas and are dauntless to make a change.
If someone is gallant, they behave bravely and honourably in a dangerous or difficult situation.
The gallant soldiers lost their lives so that peace might reign again.
第一个意思是：adj.（对女子）殷勤的，彬彬有礼的 【If a man is gallant, he is kind, polite, and considerate towards women.】
Douglas was a complex man, thoughtful, gallant , and generous.
第二个意思是“adj.顽强的；奋力的 ”【A gallant effort or fight is one in which someone tried very hard to do something difficult, although in the end they failed.】
He died at the age of 82, after a gallant fight against illness.
If you are game for something, you are willing to do something new, unusual, or risky.
①After all this time he still had new ideas and was game to try them.
②He said he's game for a similar challenge next year.
当然“game”也有对应的副词形式：gamely 表示“勇敢地；顽强地 ”【If you do something gamely, you do it bravely or with a lot of effort.】
Mary Ann smiled at her gamely .
If you say that someone has an indomitable spirit, you admire them because they never give up or admit that they have been defeated.
①Demonstrating indomitable courage, he fought to regain the use of his legs, particularly through swimming.
②A selfless man has an indomitable spirit.
If you describe a person or their actions as heroic, you admire them because they show extreme bravery.
His heroic deeds were celebrated in every corner of India.
再补充一个：它的名词复数形式“heroics”表示“（愚蠢或危险的）逞英雄行为”【If you describe someone's actions or plans as heroics, you think that they are foolish or dangerous because they are too difficult or brave for the situation in which they occur.】
He said his advice was: 'No heroics , stay within the law'.
If someone, for example a sick child, is described as plucky, it means that although they are weak, they face their difficulties with courage.
The plucky schoolgirl amazed doctors by hanging on to life for nearly two months.
A valiant action is very brave and determined, though it may lead to failure or defeat.
Despite valiant efforts by the finance minister, inflation rose to 36%.
If you describe someone as venturesome, you mean that they are willing to take risks and try out new things.
And in all honesty, I confess that this venturesome excursion was far from displeasing to me.
Someone who is gritty is brave and determined.
①We have to prove how gritty we are.
②A gritty determination to avoid humiliation.
gritty这个词，其实它的本义是“含沙砾的；覆有沙砾的；沙砾般的 ”【Something that is gritty contains grit, is covered with grit, or has a texture like that of grit.】
The sheets fell on the gritty floor, and she just let them lie.
“gritty”还有另外一个意思，表示“（对艰难或令人反感的情形的描述）逼真的，真实的，活生生的 ”【A gritty description of a tough or unpleasant situation shows it in a very realistic way.】
His most celebrated work is the film classic, 'Woman in the Dunes,' a gritty look at survival in an extreme environment.
这里再补充一个词：nitty-gritty 表示 本质;实质;基本事实 【If people get down to the nitty-gritty of a matter, situation, or activity, they discuss the most important, basic parts of it or facts about it.】
The city's newspapers still attempt to get down to the nitty gritty of investigative journalism.
Someone who is adventurous is willing to take risks and to try new methods.
Warren was an adventurous businessman.