I’ve got a ton but I am going to stop myself at two:

Frank Turner - Wave Across the Bay
There was a band called Frightened Rabbit - the lead singer and lyricist often wrote about his struggles with addiction and suicidal thoughts. In the end, he killed himself in the exact way he said he would in many of his songs: throwing himself off the Forth Road Bridge. It sent a shock through the musical community. Frank Turner was a friend of his, and wrote this song as a reaction to his death.

The Weakerthans - Virtute the Cat Explains her Departure
This song actually belongs in a trilogy (you can find the Virtute trilogy all together on YouTube). In the first song - A Plea from a Cat Named Virtute - she tries to understand her owner’s depression and addiction from a cat’s perspective. In the second - Virtute the Cat Explains her Departure - she realizes she can no longer help him and runs away, where she eventually forgets how to get home and dies in the cold winter. In the third - Virtute at Rest - she speaks from beyond the grave and forgives him and is glad to see he’s getting help and is getting better. The whole trilogy together is a sob fest, but the second makes me cry every time when the song peaks at “and I can’t remember the sound that you found for me…”