Both Uses

caustic
in
Doctor Zhivago
(Edited)

They did this by saying unpleasant things to each other, their conversation becoming increasingly caustic until an emotional storm burst and soon ended in tears and a reconciliation.
Chpt 1.2 *

caustic = harsh or critical
With a passionate haste, she looked around her at the crowd, with eyes as smarting, unseeing, and tearful as if an oculist had put caustic eye-drops into them, and all the people began to move, shuffle, and walk out of the room, leaving her at last alone, behind half-closed doors.
Chpt 2.15 *

caustic = damaging or harsh

Definitions:

(1) (caustic as in: a caustic chemical)
damaging or harsh -- often of a corrosive chemical like a strong acid
(2) (caustic as in: a caustic person)
sarcastic, critical, or harsh
(3) (meaning too rare to warrant focus)