Suggest me fictional books about self-destructive geniuses

Hello! I am searching for the single novels, probably European or American classics. I am grateful for any help!
Main hero possible prototypes: Dr. Greg House, Sherlock from BBC episodes, hero from "Million little pieces", and other miserable and tragic guys who are self-destructive.
I also wanna add that I have read a little similar classics to my request as "Great Gatsby", "One Flew Over the Cuckoo's Nest", "Martin Eden" and a lot of others. I wanna probably open new classic authors for me (I am familiar with Hemingway, Fitzgerald, Kerouac, Malcolm Lowry, Burroughs, London and others).
With plot like this: supporting character / the narrator is not special or very smart but he is good, loving and just reliable. And he has a best friend (main hero). And they haven't seen each other for a long time. And the main hero is a genius or at least very talented person, he seemed to be happy and successful. But when the narrator somehow meets his friend again he discovers that something is terribly wrong to him. At some point we understand that main hero is an alcoholic (or a drug addict). There can be kind of phrase – "I was looking into his eyes. I couldn't see my best friend there. They were drunk and empty". So this supporting guy decides to help his friend – any good way – clinic, rehab, psych ward and so on.
This story can be dramatic or tragic. Probably there is not one supportive character but a found family. But this story focuses on friendship, acceptance and addiction.
Besides, I am very interested if this self destructive main character works as…
1. Journalist (like "Last Summer in the city" by Gianfranco Calligarich, "Barfly")
2. Police officer or detective (Heard about "A Scanner darkly", "Dark Matter")
3. Idk, some lonely guy from dark fantasy (Honestly, I don't know anything about fantasy. I have read only "A night in the lonesome October" by Zelazny, the trilory "Inkheart" by Funke. But I am not a big lover of series. Probably here you can know something interesting and unusual.)
4. Writer (like in "On the road") /screenwriter (like "Permanent Midnight", "Leaving Las Vegas")
5. Circus performer (the owner of the circus can be cruel and unholy. But anyway this performer has found family)
6. Just be a genius
Anyway, thanks for your help!