cruel             
adjective uk/ˈkruː.əl/ us/ˈkruː.əl/ crueller | cruellest or crueler | cruelest
B1 残忍的;残酷的;刻毒伤人的
extremely unkind and unpleasant and causing pain to people or animals intentionally
  Don't tease him about his weight - it's cruel. 别拿他的体重开玩笑——这样太刻薄了。 
 Children can be very cruel to each other. 小孩相互之间会很残忍。 
  令人痛苦的
causing suffering
  His death was a cruel blow. 他的死是个无情的打击。 
 - More examples
 - It's so cruel to keep a pony chained up like that all the time.
 - Can't you see that you're really frightening your little brother? Don't be so cruel.
 - We appear to have been the victims of a cruel practical joke.
 - Fate played a cruel trick on him when he was badly injured in his first international game.
 - Keeping animals in these conditions is unbelievably cruel - the farmer ought to be prosecuted.
 
cruelly
adverb uk/ˈkruː.ə.li/ us/ˈkruː.ə.li/
B2 残酷地;残忍地
in a cruel way
 Idiom  
be cruel to be kindidiom  虽让人痛苦却有所帮助;忠言逆耳,良药苦口
to do or say something that causes someone pain because you believe that it will help them