如果说一个人很坚强，“坚强”用那个单词最合适

He is firm in character 他性格坚强。

strong

TOUGH

is better than any other words!

staunch; resolute; adamant; hardy; rigid; sturdy

tough
a.
1. 坚韧的,牢固的,折不断的
This material is as tough as leather.
这料子像皮革般坚韧。
2. (肉等)老的,咬不动的
The steak was so tough I couldn't eat it.
牛排太老了,我咬不动它。
3. 强壮的,结实的
Donkeys are tough little animals and can carry big loads.
驴是结实的小动物,能负重载。
4. 顽固的,固执的
He is a tough nut.
他是一个顽固的家伙。
5. 不屈不挠的,刚强的
He is a very tough man.
他是个硬汉。
6. 粗鲁的;不守秩序的,无法无天的
He lives in a tough neighborhood.
他住的地区邻里非常粗野。
7. 【口】不幸的,倒霉的[(+on)]
A spell of tough luck discouraged us.
一阵坏运气令我们大为沮丧。
8. 棘手的,费劲的
That was tough work.
那是棘手的工作。
9. 强硬的;严格的;冷酷的[(+with/on)]
The law is tough on offenders.
该法律对违法者处罚很严厉。
n.
1. 【美】粗暴的人;暴徒,恶棍[C]
A gang of toughs attacked the police.
一群暴徒袭击了警察。

以上结果由 Dr.eye译典通字典 提供