big, deep, deep-seated, genuine, great, intense, overwhelming, pure, real, terrible, utter
My biggest fear was that my children would get sick.
It was the first time she had experienced real fear.

worst
growing
general, widespread
constant, nagging
the constant fear of discovery

irrational, unfounded, unreasonable
Our fears proved unfounded.

legitimate, well-founded
primal
the most primal fear, that of death

mortal, paralysing/paralyzing
public
Public fears about the disease increased.

childhood
the girl's childhood fear of being eaten by monsters

experience, feel, have
She did not know why she should feel such fear.

be filled with, be gripped by, be paralysed/paralyzed by, be paralysed/paralyzed with, tremble with
express, show, voice
The boy showed no fear.
Doctors have voiced fears that we may be facing an epidemic.

confront, face
cause, inspire, instil/instill
the fear that her mother had instilled in her

fuel, heighten, raise, stoke
This incident will fuel fears of a full-scale war.
This stoked fears of financial difficulties.

exploit
confirm
My worst fears were confirmed.

allay, alleviate, assuage, calm, conquer, dispel, ease, overcome, quell
The government is anxious to allay the public's fears.
She managed to overcome her fear.

hide, mask

abate, subside
When she heard the news, some of her fear subsided.

grow (esp. BrE)
Fears are growing of a new oil embargo.

grip sb, haunt sb, overcome sb
A sudden fear gripped him.

course through sb, wash over sb, wash through sb
strike sb

for fear of
Nobody refused for fear of being fired.

in fear
He ran away in fear.

in fear of
The men hesitated in fear of whatever was to come next.

out of fear
He lied out of fear.

through fear
The students obeyed through fear of punishment.

with fear
His face was white with fear.

without fear
She stared at him without fear.

fear about
his fear about what might happen

fear for
my fear for her safety

fear of
They have a terrible fear of failure.

fear over
new fears over terrorism

fear and loathing
fear and trembling, fear and trepidation
The men set off in fear and trepidation.

live in
The people live in fear of attack by the bandits.

strike fear into (the heart of) sb
The sound of gunfire struck fear into the hearts of the villagers.

genuinely, greatly, really
This disease is greatly feared.
I really feared that this might be the end.

rightly
Everyone rightly feared the coming war.

seem to
begin to
learn to
He learned to fear and respect this force of nature.

for
We feared for their safety.

have little to fear, have nothing to fear
You have nothing to fear from him.

have reason to fear sth
have no reason to fear sth

Fear is used with these nouns as the subject:
critic, expert

Fear is used with these nouns as the object:
answer, backlash, consequence, death, effect, failure, persecution, rejection, repercussion, reprisal, retaliation, retribution, worst, wrath