Does a righteous intention invalidate a corrupt act, and does a corrupt intention rectify a righteous act?

A good intention does not rectify a corrupt act, but it elevates a permissible act to the level of an act of worship and obedience, as is the case when a man approaches his wife with a good intention. As for a corrupt intention, it invalidates a good deed. An example of this is a man fighting out of ostentation and bravery, and not so that the word of Allah may be supreme.