His besetting sin is laziness.

他所易犯的毛病就是懒惰。

youdao

Their besetting sin is curiosity and they get themselves into trouble because they snoop in places where they shouldn't."

VOA: special.2009.08.24

Fundamentally, the besetting sin of American academia is not celebrity professors but hyper-specialisation.

ECONOMIST: Celebrity professors are a good thing. Really

But because voluntary work would be encouraged and organised by the government, it avoids the let-them-eat-cake indifference that can be the besetting sin of the right.

ECONOMIST: Lexington