punching bag
n//ˈpʌnt͡ʃɪŋ ˌbæɡ//boxningssäck, sandsäck, slagpåse
A tough bag, usually cylindrical, filled with air, sand, or other material, often suspended so that it swings freely, which is punched or kicked when practising sports such as boxing or martial arts.
(figuratively) A person serving as an object of abuse.