Is insulting one's wife with foul language, with the intention of teaching and disciplining her, knowing that what was said is untrue, considered unlawful and deserving of accountability from Allah, even if the husband intends to repent and apologize later?

A husband is commanded by Islamic law to treat his wife kindly. Insulting or cursing her contradicts this. Accusing one's wife falsely is a grave matter. If it was a slip, it should be overlooked. If it was a serious matter, then it has its legitimate ways of being addressed. Good intentions do not make a bad deed good, and intending good through evil is another evil.