A doctor can kill millions if they stuff up, that's what happened before doctors were professional and epidemics such as the plague abound. If they intentionally create a bug that is resistant they could cause the deaths of millions. I think they are worth all the credit and dollars they can get considering the ethics that control the worldwide medical profession.
Every time a planes flies, ship sails, train departs a bus pulls off the corner a number of people have direct control over whether the number of individuals inside survive the day. All these vehicles have the chance of being in a position that would ensure all inside do not make it to the next day. We all do our best to make sure this does not happen.