In many American states and the federal level, we execute murderers. The Bill of Rights plainly permits this. Executing drug dealers isn't over the line either if we consider the number of people killed by drugs and the drug trade, and if we make a regular habit of it.
As for flogging people, this is arguably less cruel than imprisonment and is a good option for the sort of criminals the public doesn't need to be protected from (not suitable for violent criminals who will likely reoffend.) It doesn't keep people away from their families for years, let's them stay current in their job training, etc. It is nevertheless a strong deterrent but it does less damage to the rest of society.
Singapore gets results and most of their policies don't violate the letter of Bill of Rights except in a purely subjective sense, but most people in America aren't ready to give real progressive reform serious consideration.
