1.cruel作为形容词具有评价意义。其基本意思是表示人的某种性格特点,即置别人的痛苦于不顾,甚至以目睹他人遭受痛苦或使他人遭受痛苦为快。
2.cruel在句中可用作定语或表语。作定语时主要修饰表示人的名词,也可修饰疾病、战争、命运等抽象名词。作表语时,其后可接由to引起的介词短语,表示“对…残酷”; 也可接动词不定式(短语),表示根据某一行动而评价某人是“残酷〔忍〕的”,这时的主语与动词不定式呈逻辑上的主谓关系。

cruel to be kind
忠言逆耳 help sb by using unpleasant methods
I had to be cruel to be kind and warn him that he'd lose his job if he didn't improve his performance.我只得忠言逆耳地警告他,如果他的表现不改进的话,他会失业的。

用作定语
▲～+n.
The cruel man beat his wife.那位狠心的男人打自己的妻子。
The cruel woman threw the boy into a dark room.那个残忍的女人把那孩子扔到一间黑屋里去。
His cruel master nearly beat him to death.残忍的主人差点把他打死。
The cruel master beat his slaves mercilessly with a whip.残暴的奴隶主用鞭子狠心地抽打奴隶。
It was a cruel lesson.这是个惨痛的教训。
Fate dealt him a cruel blow.命运给他以惨痛的打击。
He was criticized for his cruel acts.他因行为残忍而受到了批评。
The cruel war caused great disasters to the people.残酷的战争给人民带来了巨大的灾难。
What a cruel sight it was!这是一个多么悲惨的情景!
“How dare you say I'm unfair?”said Mr. White in a cruel voice.怀特先生恶狠狠地说:“你竟敢说我不公平!”
用作表语
▲S+be+～
 Anyone who likes watching people suffer is cruel.喜欢看别人受苦的人都是残酷的人。
How could he be so cruel?他怎能这样无情呢?
Tigers are cruel by nature.老虎生性残暴。
The disappointment was cruel.失望是令人痛苦的。
The summers there are really cruel.那儿的夏天真热得够呛。
▲S+be+～+prep.-phrase
They were very cruel to their prisoners of war.他们对待战俘很残酷。
A mother who is cruel to her child is unnatural.对自己的孩子残忍的母亲是不近人情的。
Don't be cruel to animals.别虐待动物。
▲It is/was+～+(of sb) to-v
It was cruel of her to kick her sick mother out.她把患病的母亲赶出大门,真是残忍。
It was cruel of him to say that.他说那话真是狠心。
It was cruel of them to make the donkey carry such a heavy load.他们让驴子驮那样重的东西,真是残忍。
It was cruel of Tom to tease that little boy.汤姆嘲弄那个小男孩是很残忍的事。
It is cruel to hit a dog with a stick.用棍子打狗是残忍的行为。

cruel, brutal
这两个词的意思都是“残忍的”,其区别仅在于程度上。后者表示“极度残酷”,语义比前者强得多。例如:
Murder is a brutal crime.谋杀是极残忍的罪行。

这样做真残忍。
［误］  It was very cruel doing so.
［正］  It was very cruel to do so.
［析］  cruel后可接动词不定式,但不接动名词。

在句型It is/was ～ of sb to-v中, of后的sb 指该句所谈及的对象,形容词cruel表示讲话者对这个对象的行为(即动词不定式)的评价。这种结构还用于许多其他形容词,如kind, brave, careless, clever, stupid等。注意这一句型中的动词不定式如根据上下文不言自明,则可省略。例如:
It was very cruel of you.你非常残忍。
另外,本句型中的介词of不可误用为for。

［同义词］   bitter, hard, merciless, ungentle, unkind
［反义词］   kind, merciful
［词源］ ＜古法语、拉丁语cruclelis(残忍的)