regrettably

1 ENTRIES FOUND:
regrettably /rɪˈgrɛtəbli/ adverb
regrettably
/rɪˈgrɛtəbli/
adverb
Britannica Dictionary definition of REGRETTABLY
[more regrettably; most regrettably]
1 
— used to say that something is disappointing or regrettable
2 
: to an extent that causes disappointment or regret