Dilaudid is a brand name for hydromorphone, one of the most potent narcotics regularly prescribed for human use. When it's sold as a powder for recreational use, it can cause overdose when people believe that it's heroin. The only stronger ones that I can think of are Opana (oxymorphone) and fentanyl (which wears off much faster than most pain killers).

Oxymorphone is generally used only for cancer patients, while fentanyl is used for breakthrough pain. I was actually prescribed oxymorphone in the hospital as a teenager when I nearly lost my foot to a combination of an autoimmune disorder and antibiotic resistant staph. There's not a whole lot of the three days I was on it that I can remember. It was hard to tell whether I was awake or asleep, and I apparently scared the absolute hell out of my parents by telling them that I was going to miss them, because I was going to die soon. Apparently, I thought that I could comfort them by telling them that I knew I was going to go to Heaven, so it was okay. I also apparently threw up a lot.

I imagine that hydromorphone is similar. I don't particularly want to find out, honestly.