silver bullet
US /ˈsɪl.vər ˈbʊl.ɪt/
UK /ˈsɪl.vər ˈbʊl.ɪt/

1.
a magical solution to a difficult problem
:
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There's no silver bullet for solving poverty; it requires a multifaceted approach.
•
Everyone is looking for a silver bullet to fix the economy, but it's more complex than that.