Far Cry 3 Blood Dragon Classic Edition

Not that tough really, wait until later in the game when you've upgraded your weapons a bit.

I used the Machine gun and got a dragon down to nearly 0 health. Just keep shooting him until the last bit of white disappears from his health bar (When he's low don't shoot him in the purple patch or you may accidentally kill it)

When the green bar is empty just unload arrows into it (They can't be upgraded during the game) so it may take a few. It took me approximately 10 arrows once his bar was empty to kill him. It might not look like you're damaging it but you are just at a very slight rate.

This may seem impossible at first, but you can earn it once you reach the first Garrison in the game. As the dragons can’t enter the Garrisons unless you disable the barriers stopping them, you can take advantage of cover within the base. To earn this with ease you can reduce the dragons health with any weapon or explosives, you just need the final blow to be with the arrow.

As arrows do little to no damage to this enemies, aim for the heart, or the big purple mark on their chest. It may take several arrows to kill the dragon you’re fighting, but this is the most straight forward way.

(Copied from version Xbox360 - Fizzmatix Solution)