https://wccftech.com/red-dead-redemption-2-changes-to-difficulty/

Red Dead Redemption 2 is far from being the most difficult game around, so if you are looking for a challenge, you won't find it there. Unless you use a mod that has been released recently which allows for some changes to the game's difficulty.

The Difficulty Scaler mod allows players to change the damage values for all weapons for both player and AI enemies. The mod is quite easy to use and features controls that allow players to revert back to vanilla settings with a hotkey.