The concept that large reward requires large risk does not apply to many trading methods.
Serious options traders have minimum risk for potentially large reward, but since I no longer trade options I'll leave others to comment if they so wish.
My own US intraday trading is based on minimum risk and maximising reward. I'll enter many positions with a risk of 5 - 8 cents, sometimes the reward is only 15 - 30 cents but often turns into 100 - 120 cents. Certainly that appears a risk/reward which is virtually "off the scale" to the mindset of most traders, but I, and many others, do it every day. What is more, it is done with a high percentage hit rate - it is NOT a matter of lots of small losses and a few large gains, it is about reading the market properly, minimising risk, and then very good position management producing a few losses, a few scratch trades, and many profitable ones ranging from small to very large rewards.