I had a dog die from liver failure directly linked to her eating chocolate.
We were showing the house, and she was left out of her crate one day, the realtor who showed the house locked her in the pantry. She found a couple boxes of extremely rich chocolate and ate all of it.
Just that incident damaged her liver so badly that she had to be on a special diet for the rest of her life, until she finally died of liver failure. She was a West Hyland White Terrier who weighed only 18 lbs. RIP Chloé.