Tā de guāndiǎn hěn duō, yī yán yǐ bì zhī, jiùshì fǎnduì gǎigé.
He made many points; to sum up, he opposes the reform.
Tips
history
Directly from 《论语·为政》: 《诗》三百,一言以蔽之,曰‘思无邪’ — Confucius boils down all 300 poems of the Shijing into a single phrase (思无邪, 'thoughts without depravity'). The idiom has been used for the same rhetorical move ever since.
register
Formal and literary. Sentence-initial: 一言以蔽之,... introduces the summary. In casual speech, 总而言之 or 简而言之 are more common equivalents.