unregretful

adjective

1. full of regret; sorrowful because of what is lost, gone, or done.

adj.1640s, “full of regret,” from regret + -ful. Regretfully, properly “with regret,” incorrectly used in place of regrettably “it is to be regretted that; calling for regret” since at least 1965. “A regrettable use, prob. after HOPEFULLY adv.2” [OED].