to make something seem less good 减低，破坏，损害:
They worried that the scandal would seriously detract from [=diminish, hurt] her chances for reelection.
他们担心丑闻会严重影响她重新当选。
The overcooked vegetables detracted somewhat from an otherwise fine meal.
蔬菜烧得过熟，否则这就是顿美餐了。