他仁慈、亲切，但非常严肃。

Serious: He was kind and affectionate, but very serious.

youdao

他在我眼里是个非常严肃但友好的人。

He struck me as a very serious but friendly person.

《柯林斯英汉双解大词典》

肯恩：吉姆的外表看起来像个商人。他常常穿剪裁合身的西装，但事实上他是一位非常严肃的学者。

Ken: in appearance Jim looks like a businessman. He wears a lot of well-tailored suits. But he's really a very serious scholar.

youdao