The last 5 or 6 Presidents. All handed out massive numbers (George Bush's pardoning of "only 77" was seen as rather shocking) of pardons/rescinded They all pardoned/rescinded the sentences of people who committed heinous crimes up to murder, terrorism, attempted assassination, and treason/espionage in some cases
Thank you for bringing it up, gave me a reason to look over the listing of pardoned offenses.
For the moment, I just looked through George W. Obama, and George H.W Because Clinton, Regan and Carter's lists are much longer. They may be different, but you did use the word "all" so I think an observation of three lists is pretty valid.
Now I did speed read, so I may have missed something, but I did not see a single murder, act of terrorism or attempted assassination pardoned by those three. It was sort of interesting to see what did get pardoned.
Things that came up repeatedly were various kinds of fraud and dishonesty involving taxes, to be expected. Embezzelment, I figured it would be there, A lot of drug crime, sort of makes sense.
A fair amount of theft of mail by postal workers, huh.
Also a number of statutes specific to the production, distribution, sale and taxation of alcohol, that was surprising.
The vast majority was in the realm of white collar, or at least non-violent crime. There was one involuntary manslaughter, two bank robberies (pardoned by different presidents) and a couple burglaries on indian reservations. If there are other exceptions I missed, there are still very few.