Collocations for onset - noun

rapid, sudden
the sudden onset of the disease

acute (medical)
Symptoms include the acute onset of pain.

slow
early
delayed, late

delay
prevent
mark, signal
His first hit record marked the onset of an astonishing career.
The development of pubic hair signals the onset of puberty.

after the onset
after the onset of sleep

at the onset
at the onset of the war

before the onset, prior to the onset
since the onset