big, bitter, deep, genuine, great, profound, real, sincere
Her biggest regret was that she had never had children. | She expressed deep regret at the incident.

pang, stab, tinge, twinge

feel, have
I have absolutely no regrets about resigning.

express, show

to your ~
To my regret, I lost touch with her years ago.

with ~
It is with deep regret that we announce the death of Mr Fred Fisher.

without ~
She thought of them without regret.

~ about/over
She showed no regret about leaving her country.

~ at
my sincere regret at what has happened

~ for
She enjoyed living alone, but felt a tiny pang of regret for her mother''s cooking.

expression of regret
The police offered no expression of regret at his wrongful arrest.

a matter for/of regret
I never learned to play an instrument and that''s a matter of some regret.

bitterly, deeply, greatly, really, very much
The president said that his country deeply regretted the incident.

rather | immediately, instantly
I immediately regretted not asking for his name and address.

later
Pierre told them some things he later regretted telling.

never

begin to | come to, live to
She knew that she would live to regret this decision.