德性 (déxing): moral integrity; virtue (formal…

Two readings, two meanings. Formal 德性 (déxìng) = 'moral character' — used in classical/philosophical writing. Colloquial 德性 (déxing, neutral tone) = 'pathetic/disgusting manner' — almost always sarcastic or mocking. Don't mix them up: praising someone's 德性 with the colloquial tone reads as an insult.

register

The colloquial sense is often paired with 那副 (nà fù, 'that look of'): 那副德性 = 'that pathetic look.' Common in northern dialect speech.