I ALWAYS RECOMMEND TO USE THE OPENIV MOD FOLDER METHOD, IT'S SAFER, CLEANER, BETTER

MORE INFORMATIONS CAN BE FOUND HERE : http://openiv.com/?p=1132

1. Start OpenIV
2. Navigate to Grand Theft Auto V\update\update.rpf\common\data\effects\peds
3. Activate edit mode
4. Replace (you can just drag and drop) peddamage.xml with the one coming in this archive
5. Disable edit mode

A backup file is included. 

