In situations where a character is an irredeemable and unrepentant villain (pedophile) but is just a regular everyman character in every other respect (he looks, acts, and speaking in an unremarkable way, doesn't have a dark back story, and there is no in universe attempt to justify his actions as being down to some form of trauma,) what literary factors or story telling techniques can be used to make him seem relatable to the audience who is fully aware of what they are?
The overall premise is the story of an unremarkable everyman trying to find evidence that another unremarkable everyman pretended to be a teenager online in order to entice local school children to send him indecent selfies.
Although the story features an obvious antagonist and an obvious protagonist in the traditional sense, the main character is a neighbor who knows both of them, and who acts an an audience surrogate. He sees events happening from the outside, and witnesses events rather than participating in them (he has zero agency.)
The story is viewed in hindsight after the events of the story have concluded and all the secrets have been revealed, with the main character (audience surrogate) mentally reviewing things that have already occurred trying to put the pieces that he was aware of into context.