I promise this is an honest question: has ANY president since the civil war reconciliation blanket pardoned someone for an entire decade for all known and unknown federal crimes?

There's a pretty big obvious example.

https://en.wikipedia.org/wiki/Pardon_of_Richard_Nixon

> Now, Therefore, I, Gerald R. Ford, President of the United States, pursuant to the pardon power conferred upon me by Article II, Section 2, of the Constitution, have granted and by these presents do grant a full, free, and absolute pardon unto Richard Nixon for all offenses against the United States which he, Richard Nixon, has committed or may have committed or taken part in during the period from January 20, 1969 through August 9, 1974.

That is damn close. This one is quite interesting in and of its twice as long and concerns someone who doesn't have the kind of immunity presidents have recently been under scrutiny for possibly having.

Another interesting thing I found about Hunter's pardon was that the president openly said isolated prosecutions of lying on the 4473 are unfairly targeted, but then baffling only pardoned his son for it.

Ford. For Nixon.

Not quite a decade, and not as broad in terms of what crimes are covered, but much bigger in terms of scope:

https://en.wikipedia.org/wiki/Proclamation_4483