na-adjective
abnormal; perverted
Often used for sexual deviance or perversion, but can also describe general abnormality in a technical or colloquial sense.
彼の趣味はちょっと変態的だ。
His hobby is a bit perverted.
その生物は変態的な成長をする。
That organism undergoes abnormal growth.
異常 is a more general and neutral term for 'abnormal' or 'unusual', without the sexual connotation often carried by 変態的.
Derived from 変態 (metamorphosis, abnormality, perversion) + 的 (-like, -ish).