It might sound weird, but the two characters that I feel sorry for are :-
1. Asou Seiji (From the Moonlight Sonata Murder Case) : He was away from the death of his parents and sister, first consumed by the mystery. Then by the guilt of unknowing, then by revenge as he felt it was his duty to punish the men who punished his parents. More to that he was fully conscious while doing the murders and did not want to do them but felt obliged, plus he seemed to live for the sole purpose of doing that being the only culprit to commit suicide in front of Shinichi/Conan, plus he had to impersonate as a woman to get his revenge, plus his name Seiji first struck me as someone who is as incredible as Shinichi, don't know why..
2. Tatsuya Kimura (From the Karaoke Box Murder Case) : The man was in love in it's purest form, and had to suffer from the love he had. It's not unconditional love, but he did love her after what she did and yet he was unable to put his feelings into words and had the burden to keep his closest friends away so they won't miss him dearly. But it is his love that echos pain in a romantic relationship, in which a lover is unable to confess and lives with pain while the loved one is very very nearby..Sorts of like Shinichi, but he was heartbroken of the girl's attempt to change herself.