What unethical experiment would have the biggest positive impact on society as a whole?

Genetic engineering, imo. To make humans more resilient. All it takes is a poke for someone to bleed out. Tougher skin, redundant organs, bones as strong as steel, better immune system response, longevity, intelligence, increased empathy or reduced aggression, advancing human instinct by 20,000 years, so it can catch up to our modern development, etc, etc. Could have a lot of positive impacts, I think.