He is a very determined and strong-willed person.

他是个很有决心和毅力的人。

《柯林斯英汉双解大词典》

When someone talks about a David and Goliath, he means that a smaller, or weaker, person is trying to fight a very large and strong enemy.

当某个人谈到大卫和歌利亚，他的意思是一个小个的人，或弱者正在打败一个非常高大和强壮的敌人。

youdao

But now I come to realize that however strong-willed a person is, he will be weak at some time, or at some point.

但是，如今我意识到，无论一个人再怎么坚强，他总会有脆弱的时候或是弱点。

youdao

Now, if we listen to that message over the next two years, given the foundations that we've got to build on, given Gordon's enormous strength - and I do believe he is a strong person for a very difficult role - we can turn this around.

BBC: Rocky times

According to Dr Fehr, a person is a strong reciprocator if he is willing to sacrifice resources to be kind to those who are being kind, and to punish those who are being unkind.

ECONOMIST: Human behaviour