My first love while reading was Ronan, but I also loved Kavinsky a whole lot, so here's an angsty/sad Ronan/Kavinsky fic: i think i made you up inside my head by coxcomb.

Alternatively, here's a dirty and semi-fucked-up Ronan/Kavinsky smut fic that is very satisfying lol: owned by Crybabydraco & mee4ever.