Shameful describes behaviour or actions that are so bad someone should feel ashamed — whether they do or not. The word judges the deed, not the feeling inside the person. A shameful lie, a shameful waste, a shameful way to treat a guest: the speaker is saying this should not have happened, and decent people would blush at it. It is stronger than just bad or wrong; it carries a moral slap. You can use it in serious talk (a shameful chapter in a country's history) and in everyday scolding (That's shameful!). Though actually, English learners often want it for the person who feels the shame. That person is ashamed. The action is shameful. A shameful man, in careful English, is a man whose acts deserve shame, not a man who looks sorry.