They shall be like mad men: The pronoun They refers to the persecutors, not the victims. In this context the adjective mad means “crazy, insane.” Good News Bible translates mad men as “wild people,” but we prefer the English idiom “wild animals,” often used of people who are out of control, behaving in a violent manner. Translators should look for an expression in their languages which clearly carries this meaning. This clause may be rendered “Their persecutors will act like they are insane.”
Sparing no one may be translated “showing no mercy to any of them.”
But plundering and destroying those who continue to fear the Lord: Plundering means “taking possessions by force.” Destroying here means “killing.”
Here is a possible model for this verse:
• The persecutors will act like wild animals [or, as if the have become insane], killing anyone who continues to fear the Lord and plundering their possessions. They will spare [or, show mercy to] no one.
Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on 1-2 Esdras. (UBS Helps for Translators). Miami: UBS, 2019. For this and other handbooks for translators see here.