The ideal solution would be to tie the rope directly to the stake at the pivot point under the ground. This would force the stake to be pulled completely through the ground before it would fail.
Unfortunately, by the time you dig out the soil in order to run the cordage to the stake, all the cohesive tension that exists in the soil is broken. In short, the stake would pull through the soil very easily.
There are a number of anchoring systems available that attempt to address this shortcoming - each with their strengths and weaknesses. Many have been discussed in other threads already.
The solution that I have developed is called a stake boom.