Larian Studios Forums Divinity: Original Sin 2 Divinity - Original Sin 2 - General New hard difficulty

The easiest way would be to leave all existing Difficultly Modes as it is and add a new Impossible Mode.
Just edit the Enemy Characters for "Impossible Mode" and give them

(new) Impossible Mode

+50% more Damage for Enemy Characters
+50% more Armor Rating for Enemy Characters
+50% more Vitality for Enemy Characters