If you pay $1000 to buy shares in a particular stock and the share price doubles, you will have made a profit of $1000, or 100%.
The most you could have lost would have been $1000, assuming the share price fell to zero, but when you sold the shares you received $2000, so the profit:loss ratio is 2:1.
But why would you let the share price fall all the way to zero? If you set a stop-loss order for your broker to sell your shares if their price fell 10%, then you would only be risking $100. In this case, your risk would have been $100, you sold your shares for $2000, so your profit:loss ratio would have been 20:1.