Shameful means so bad that it brings disgrace. Something that should not have happened and reflects badly on whoever let it.
It describes actions, conditions and records rather than people directly, so a shameful episode and a shameful waste are both standard. Keep it clear of ashamed, which describes the person feeling it, and of shameless, which describes somebody who ought to feel it and does not. That three-way distinction is worth having, since shameful, ashamed and shameless all come from the same noun and point in different directions.
1adjectiveshamefulDeserving disgrace or strong disapproval.
“The state of the building was shameful.”
Middle English
schameful
English, today
shameful
From Middle English schameful. From Middle English schameful, schamfull, from Old English sċeamfull, sċeomfull, equivalent to shame + -ful. Cognate with Danish skamfuld (“shameful, shamefast, ashamed”).
Etymology from Wiktionary, CC BY-SA