Could he pardon the parents of the 13 tortured children? Isn't his authority to pardon limitless?
The power to pardon is one of the least limited powers granted to the President in the Constitution. The only limits mentioned in the Constitution are that pardons are limited to offenses against the United States (i.e., not civil or state cases), and that they cannot affect an impeachment process.
...and he shall have Power to grant Reprieves and Pardons for Offenses against the United States, except in Cases of Impeachment.