For example, a shockingly small amount of John Calvin's works are translated into English. Regardless of what a person thinks of his theology, his influence on the rise of democracy in post-Reformation Europe and the Americas is staggering.
You can find "the essential works of John Calvin" (51 volumes, in English) here: https://www.logos.com/product/145428/the-essential-works-of-...
All of John Calvin's commentaries, letters and 'The Institutes' here (109 volumes, in English): https://www.logos.com/product/5170/calvin-500-collection
Calvin's tracts and treatises (8 volumes, in English) here: https://www.logos.com/product/5165/tracts-and-treatises-of-j...
I'm curious as to what you think hasn't been translated into English.
There was a Latin collection that contained some of these works called the Corpus Reformatorum published in the 1800s.