bitterly
US /ˈbɪt̬.ɚ.li/
UK /ˈbɪt̬.ɚ.li/

1.
bitter, fel
in an angry or resentful way
:
•
She complained bitterly about the unfair treatment.
Ze klaagde bitter over de oneerlijke behandeling.
•
He bitterly regretted his decision.
Hij had bitter spijt van zijn beslissing.