This achievement is story-based and will unlock automatically while you progress through the game.
TrafficKing is the second major "boss" you'll fight in the story. The key to defeating him is to activate the four pillars you stand in the middle of and make sure TrafficKing is also INSIDE this area so he is electrocuted. This is when he's vulnerable enough to attack. I'd recommend using your Enhanced Reflexes/Slow-Mo ability (fifth ability on the right) in order to dodge his shots with ease.
Hope this guide helped. If you have any questions or concerns, lemme know!