There's no such way of earning the best return without taking the highest risk. If you want to take the best returns then you should be ready on taking the highest risk. But if you are relaxed on taking up the lowest risk then don't expect that it will give you the best and highest profit. As of now, I can only think about trading.
Sometimes still peoples think they need a method which get big profit with small risk which clearly hard to find. Even on trading, sometimes there are huge crash and leads you to loss. That's okay to take high risk because one day you would earn bigger.