Ride to Hell Retribution

I personally just unlocked this in about 25-30 minutes starting from scratch. What I did was played on Pretty Boys level, fourth mission on the board (key with a cross hanging). It starts on foot in the graveyard. Finish that fight, then go to the riding section. Almost immediately, you will have 3 cops on you as you cross the bridge. This is where I was earning a rage kill on the bike every time. Aim for headshot kills on 2 of the cops. The 3rd should then have a B button prompt above his head. Follow the QTE to earn a Road Rage attack on your bike. Then continue riding until you see the autosave icon (when you go offroad for the second time). From here you can go into Load/Exit and Restart Current Mission to start off right at the beginning of the riding section. Rinse and repeat until achievement unlocked.