I'm sorry but this is simply untrue. Please, don't spread misinformation.
20 ibuprofen will not cause liver failure within 6 hours. Paracetamol is a lot more damaging to the liver and even that can take days to kill you and that's even if you actually do die. I've taken 300 paracetamol over the course of a week before and my liver is fine. I used to take 50 co-codamol nearly every day, for a long time, and I'm still alive.
At worst, the ibuprofen will cause severe stomach ulcers and even those are very survivable.
You were right about the agonising pain though, liver failure is probably one of the worst ways to die.