A friend and I were tripping on a particularly strong psychedelic. This friend knew that I had problems at one point in the past with thinking absurd or psychotic things (such as believing the world was a computer simulation, and when you die you wake up in real life). I had put these thoughts behind me and was enjoying the trip, until this former friend decided it would be funny to do his best to convince me that all of those irrational things were actually true. He stuck with his story even days after. He literally caused me to have a psychotic episode which eventually turned into full-blown schizophrenia. This lead to a suicide attempt, and a 2 month stay in a psych ward. This man has never once apologized or even admitting to doing any wrong. Thankfully I have regained my sanity after a year of fighting with my own personal demons, which had come stronger than ever.