Who is Michael Card and John Thompson that wrote El Shaddai?

You're likely thinking of the song "El Shaddai" by Michael Card, not John Thompson. There is no known musician or songwriter named John Thompson associated with this song.

Michael Card is a Christian singer-songwriter and author. He wrote "El Shaddai" in 1977, and it has become one of his most well-known and popular songs. The song is a praise song based on the biblical name for God, El Shaddai, which means "God Almighty" or "God the Sufficient One."