Q.Will Branches On A Sycamore Tree Grow Back? And How Long If So?
Today my uncle has his sycamore tree cut. The person who cut it was supposed to just trim it but instead had cut off half way through all the branches. It was a really nice tree and now ruined. Will it grow back?

Certified GKH Gardening Expert
It is far from ruined. That tree was done a HUGE favor. Pollarding anything in the Acer genus will help keep it manageable, promote airflow, and cause a much bushier growth.
Two years from now, you will have a tree that far exceeds the beauty of an untamed tree.
Here is an article that will help you to understand what has happened:
https://www.gardeningknowhow.com/ornamental/trees/sycamore/sycamore-tree-pruning.htm