The Pardoner is a fraud, a cheat, and a charlatan who goes round selling pardons even though he has no authority to do so. Over time, he's developed quite a thriving business, and many people are prepared to pay him a bribe to avoid being punished by the ecclesiastical courts.
What's even more brazen about such blatant corruption is that the Pardoner isn't in the least bit ashamed of it. He has no qualms whatsoever in telling the other pilgrims of his sordid little sideline.
This makes it all the more remarkable, as well as ironic, that he should choose to tell a tale whose moral is that greed will always come to grief in the end. In "The Pardoner's Tale," some greedy, grasping young men end up being killed through their avarice. One of them is stabbed to death by the other two, while they in turn die a slow and painful death after consuming rat poison.
The young men in the tale are guilty of what the Pardoner calls “tavern sins,” so called because they are the kind of sins one would expect to see from patrons of a tavern. Yet the Pardoner's condemnation of these sins is hypocritical, to say the least, as he makes his living from bribery and corruption.