This is a paid asset, but now you can download Explosion Sounds Pro Free.
Detail this asset from Unity Store: Original Link
Explosion Sounds Pro v1.0
“If possible, please buy the package to support the developer”
In this pack you will find 75 professionally designed explosion sounds which were carefully mixed and mastered by a professional sound engineer.
The pack contains everything from classic/massive explosions to C4,Grenades and even EMP explosions!