For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of people who suppress the truth by their unrighteousness – Romans 1:18 (NET)
Immediately after speaking of what he understood to be the mysterious and inherent power of the Gospel (the proclamation that Jesus is Lord of all), the Apostle Paul launches into a statement concerning the pouring out of the wrath of the Creator God, and the connection of the pouring out of that wrath to ungodliness and unrighteousness. Following that lead-in, the remainder of the first chapter of the letter to the Romans is decidedly direct, as Paul, in his writing here, would seem to have in mind certain individuals or groups of people to which his words are directed. Rather than analyze in an attempt to ascertain to whom or to what situation the words from verse eighteen through thirty-two are directed, it would probably be better to take into consideration the grand narrative of the Scriptures so as to make an appropriate application.
So in looking at the eighteenth verse, and contemplating the scope of the Scriptural narrative, one could identify the verse with the presumptive parents of the human race, that being Adam and Eve. Because human beings were made in and as the image of the Creator God, it should be understood that an aspect of godliness is rightly bearing the divine image. Accordingly, ungodliness could be considered to be the failure to adequately and properly bear the divine image.
Righteousness is perhaps best defined as “covenant faithfulness” (faithfulness to the covenant, whatever that covenant may be during the course of the Scriptural narrative), and that particular trait is usually and accurately ascribed to the Creator God, though when humans find themselves attaining to righteousness, it can also be said that they are in a state of faithfulness to the particular covenant that is to govern their interactions with their Creator and their fellow man.
Unrighteousness then, conversely, is a state of not being faithful to the covenant (covenant unfaithfulness). When Adam and Eve partook of the “forbidden fruit,” in contradiction of their Lord’s command, they were not faithful to the covenant under which they were tasked to operate. Consequently, they found themselves in a state of unrighteousness. This resulted in them not being able to completely fulfill the Creator God’s intention for what was understood to be the pinnacle of His creation that bore His image, and was responsible to play the role of reflecting His glory into the world, stewarding the creation, and constantly reminding the creation of the God that was responsible for its existence.
According to the Genesis narrative, Adam and Eve, having eaten the fruit, now found themselves unable to attain to the reflection of their God’s glory for which they had been created. Thus, entering into a condition of unrighteousness, they also succumbed to the condition of ungodliness and they fell short of the glory of God. This is marked out as the beginning of sin. With this, the indication is that mankind began to lose its right knowledge of the Creator God; and with this presence of the force of sin that marred and distorted the divine image that was supposed to represent and reveal the Creator, one could say, the truth of the Creator God began to be suppressed.