All my comics are kinda in that range of depressing/melancholy
Garden Of Mold is a surreal silent 30 page comic about the lonely life of an agoraphobic man, his plants and mold.
All Broken Gods is still new but later on it will get depressing and morbid. It has occult themes such and demons and curses and is a tragedy.
Welcome Back is an old comic of mine and very, very long. It has surreal and psychedelic themes with a touch of horror and emotional trauma. It's about a dystopian dreamworld and a bunch of friends who discover it from our world.