Asphalt Legends Unite

To perform a perfect nitro, once you have any nitro available at the top of the screen, press the nitro button once to begin using nitro, and then watch the meter up top. As soon as it enters the blue zone, press nitro again to turn blue and burst forward.

In general, every single time you use nitro you should do a perfect nitro. You will be doing this literally thousands of times throughout your time with this game, so this will unlock very early.