If God had a good purpose he did not fulfill, then did he “miss the mark”? In the sense of the Greek word “hamartanw”:
“Literally miss the mark, be in error; figuratively, of offending against God, man, religious or moral law sin, do wrong, transgress” (Friberg Dictionary)
“Even the Septuagint, although the Hebrew ‘chatah’ also means primarily to miss, endeavor to reserve ‘harmartanw’ exclusively for the idea of sin: and where the Hebrew signifies to miss one’s aim in the literal sense, they avail themselves of expressive compounds, in particular ‘examartanein,’ Judg. 20:16.” Zezschwitz, Profangraec, u. Biblical Sprachgeist, p. 63f)
But if God (for example) regretted creating man, before the flood, then didn’t God “miss the mark”? He tried to do good, and did not succeed, and that is a definition the Bible gives, of sin, God calls that sinning, to set out to do good, and to miss the mark.
James 4:17 Therefore, to one who knows good to do and does not do it [not “does not attempt it!”], to him it is sin.