"Major setback" refers to a significant or big obstacle or failure that hinders progress or causes a significant decline in a situation or goal. Full definition
It was just the latest in a string of major setbacks for tar sands oil, which has become nearly as bad for corporate profits as it is for the environment. (resilience.org)
The weekend news was not economic but political as governments all over the globe suffered major setbacks. (yragharris.com)
Be sure, however, that you can safely control each new situation, as one bad experience can cause major setbacks. (professorshouse.com)