Somehow this is both heartwarming and sad. To STG Lugar, no, there isn't. But a Japanese fan did create a fake video that featured Adachi as a Social Link.
I think I'm the only one in the entire P4 fandom who never felt bad for Adachi. Or who outright just doesn't even care about him. I like this picture though.
I think a large part of it might be if you were spoiled or not, regarding him. I wasn't, and quite liked him as he seemed, really, to be a good guy.
Because of that, after the reveal, I felt quite strange regarding him. Betrayal foremost, then there's the questioning of just how -much- of what he did was his own will and how much was his being compelled to from something other than himself. It seems to largely have been his own will, but you're just not sure.
Then there's the feeling that the hesitance to attribute his actions to his own will may just be reluctance to concede a gross error of judgement made in regards to his character.
That said, there really aren't any warning signs prior to the reveal that really hint at full-blown sociopathy, so yeah.
And regarding the letter sent to point you in the right direction: genuine effort to atone, simple curiosity or a desire to get back at the entity he might feel responsible for him ultimately ending up in the slammer? Or perhaps a mixture of all the above.
tl;dr: Adachi confuses me. I'm not sure how to feel about him, and I think that's the effect that was probably being aimed for.
BUT, Thant, you are probably right. I just personally didn't care for him. He made a good antagonist but all the fandom low makes me scratch my head sometimes. Nothing wrong with it but I just didn't think I'll ever get it. But to each their own.
This...this is like almost literally how they did it in The Golden Animation. And now there is an Adachi social link in Persona 4 The Golden. Reading the comments and seeing this image, and knowing it all happened four years ago is *weird*.