Final answer:
The phrase provided is an example of a simile, which is a type of figurative language that makes a comparison to emphasize the intensity of a fight.
Step-by-step explanation:
The phrase 'Dat buck! He fight like two devils' is an example of figurative language, specifically a simile. A simile is a figure of speech that compares two different things in an interesting way, using the words 'like' or 'as'. In this case, the comparison is being made to emphasize the intensity and ferocity of the fight, suggesting that the person fights with the strength or ferocity of two devils, which is a hyperbole, an exaggeration for effect.