expression, adverb
I regret that; I'm sorry but
A formal, somewhat old-fashioned expression used to preface a statement of regret or apology. Often found in written or formal speech.
恨むらくは、このような結果になったことをお詫び申し上げます。
I regret that things have turned out this way, and I apologize.
憾むらくは
I am sorry that we could not meet your expectations.