onerous

1. ADJ If you describe a task as onerous, you dislike having to do it because you find it difficult or unpleasant. 繁重的; 費(fèi)力的[正式]

...parents who have had the onerous task of bringing up a very difficult child. …那些身負(fù)重任要養(yǎng)育一個非常難調(diào)教的孩子的父母。