It would be unkind to go without him.

甩掉他那就太不够朋友了。

《牛津词典》

Because I think anyone shouldn't be unkind to anybody else.

因为，我认为任何人都不应该恶待他人。

youdao

Because I don't think everyone should be unkind to anyone else.

我觉得每个人都不可以对人不善。

youdao

The message of the flood story also seems to be that when humans destroy the moral basis of society, when they are violent or cruel or unkind, they endanger the very existence of that society.

而洪水所表达的信息是,当人类毁掉了社会的道德根基，当人类变得暴力，残忍，这都会危及到人类社会的存在。

耶鲁公开课 - 旧约导论课程节选

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