Anything disgraceful is shameful or shocking. No matter how angry you are at your younger sister, it would be disgraceful to destroy the Lego creation she painstakingly built.
The adjective disgraceful is good for describing completely unacceptable behavior — if you do something disgraceful, you should feel ashamed about it. The internment of Americans of Japanese descent during World War II was a disgraceful episode in U.S. history. The word comes from the verb disgrace, "bring shame or reproach upon" or "a loss of grace."