I have two from work. And I can't decide which is more gruesome.
1. While doing a gravel vac on an Oranda tank [We drain a few, then start filling so the hose follows, to save time], the strainer slipped off while I was swapping the hose, and in literally 15 seconds the poor little goldfish was stuck to the very gravel vac where the tubing meets the actual plastic cylinder, and by the time I noticed and darted back to stop the siphon...there was a very loud pop, the hose filled with orange, and I still stopped the siphon. He fell out, sank to the bottom. His intestines and other various insides were spilling out [not just exposed], and his eye had burst. Worst part? When I went to scoop him out for a quick euthanasia, he tried to swim away. His intestine got stuck on a plastic decoration and was literally, and entirely pulled out. So not only did I have to remove the fish, I had to scoop out his innards from the tank. A four year old witnessed the whole thing. wompwomp. Even though it was an accident I felt so guilty about the fish, that I spent half of my break in meditation apologizing to the fish.
2. I pulled a 'dead' Salvini with both eyes missing while the other fish were still chewing at the sockets. When I removed this fish, it flopped and gasped. Again, still alive. He was prompty euthanized. But that was actually pretty shocking. Never underestimate the sheer brutality of a Salvini.