（1）It is so cruel of them to kill them with an unthinkable action.
（2）How ruthless they are to kill them with an incredible way
（3）They are so barbarous !! How can they treat them like that ?
（4） How barbarous / cruel / ruthless they are to treat them like that !
unthinkable
形容詞 adj.
1.不能考慮的, 不能接受的, 不可想像的, 難以置信的
It would be unthinkable to ask him to do that.
叫他做那件事是毫無可能的。
It is quite unthinkable that a child like him can speak a foreign language so fluently.
像他這樣的孩子居然能流利地說壹種外語, 真是令人難以置信。
2.不可能的
Defeat is unthinkable.
戰敗是不可能的。
ruthless
形容詞 adj.
1.無情的; 冷酷的; 殘忍的
The ruthless enemy killed the old lady.
殘忍的敵人殺害了那位老太太
barbarous
形容詞 adj.
1.野蠻的,未開化的,原始的
It was barbarous to treat prisoners in that manner.
如此對待犯人,真是太殘忍了。
They were guilty of the most barbarous and inhuman atrocities.
他們犯有最野蠻、最滅絕人性的殘暴罪行。
2.殘暴的,禽獸般的
3.粗野的;無教養的;無文化的
It is barbarous to call at 5 a.m.
清晨五點給人打電話是缺乏教養的行為。
4.(用語、文體)不合規範的
5.外邦的;異族的
6.(在古代)非希臘(或羅馬)的;非基督教的
7.粗聲粗氣的;粗啞的