I never doubt about your IQ.

我从不怀疑你的智商。

youdao

I never doubt that he is an unselfish person.

我从不怀疑他是一个不自私的人。

youdao

I never doubt my ability, only doubt I have no effort.

我从不怀疑自己的能力，只怀疑自己有没有努力。

youdao

In two years as the parent of a competitive chess player, I can say without a doubt that I have never witnessed any untoward behavior by parents.

FORBES: A National Tournament Fights The Evil That Chess Parents Do

I've never taken one, and doubt I will unless I'm hard up for a column.

WSJ: Yielding With a Purpose

I've never seen one minute of doubt in his mind, not one minute where he said 'I don't want to do this'.

BBC: Eduardo delight at dream comeback