The thing about villains is that villains always have their own logic, and they don't necessarily see themselves as villains. Richelieu is not a villain, in his own mind. He's doing what he needs to do.
Too much mercy... often resulted in further crimes which were fatal to innocent victims who need not have been victims if justice had been put first and mercy second.
Certainly we do not need quantum mechanics for macroscopic objects, which are well described by classical physics - this is the reason why quantum mechanics seems so foreign to our everyday existence.