na-adjective
of low character; mean-spirited
Describes a person whose nature or conduct is base, vulgar, or morally low. Often used in formal or critical contexts.
彼の品性下劣な振る舞いに皆が呆れた。
Everyone was disgusted by his low, mean behavior.
品性下劣な人間とは付き合いたくない。
I don't want to associate with people of low character.
A compound of 品性 (character, moral quality) and 下劣 (low, base). The exact historical derivation is uncertain, but it follows a common pattern of four-character Sino-Japanese compounds.