Meanings

one's dark days

dishonest person

gang of hoodlums (hooligans)

adultery

dissident element (e.g. in a political party)

misappropriation (of funds, etc.)

discontented element

getting mixed up with the wrong people

one and only

the point of an argument being unclear

long and uninterrupted (unbroken)

nuclear nonproliferation

discomfort

insufficient study

non-support

to bungle

unauthorized (computer) access

business slump

anomaly

distrust