I have some comics in my reading list that are bittersweet and tragedies.
Both of Sketchylinez comics.
I also have a heavier comic, although how sad the story is is subjective, it depends on your knowledge of mental health stuff, abuse and how empathetic you are to those things. The gist is a mentally ill character living in a bad domestic situation, surrounded by shitty people, with one of them being an ex-friend who tries to "help" but is an ignorant moron. It's not a total tragedy because the ending will be nice (Not perfect "happily ever after", but nice.), but most of the comic is going to be bleak.
Don't read this if you're under the age of 17, and are sensitive to mental health, trauma, abuse, blood, violence, mild body horror, mild self-harm, queerphobia/bigotry, profanity and substance abuse.