Shamefulness is the noun for the shameful quality of an action — the fact that it is so bad someone should feel ashamed. It names the badness as a thing you can point to: the shamefulness of the lie, of the waste, of what was done. It is a formal, rather heavy word, much rarer than shameful. In ordinary talk, people almost never need it. They say how shameful it was, or just what a shame, or the shame of it. You will meet shamefulness mainly in careful writing that wants an abstract noun. Though actually, even there, shame itself often does the same job with a lighter step.