fǎn
适得其反
shì dé qí fǎn
to produce the opposite of the desired result / counterproductive
绒衣穿反了。
róng yī chuān fǎn le
The fleece/sweater is worn inside out.
易如反掌
yì rú fǎn zhǎng
as easy as turning over one's palm / very easy