Final answer:
The rhetorical device used in the sentence is parallel structure, which shows equal importance among ideas with a similar pattern of words, adding rhythm and emphasis.
Step-by-step explanation:
The rhetorical device employed in the sentence "I will meet any challenge, overcome any obstacle, and beat any rival that comes my way" is C) Parallel structure. This device is used when similar patterns of words or phrases are used to show that two or more ideas have the same level of importance. Here, the parallelism is in the verb phrases "meet any challenge," "overcome any obstacle," and "beat any rival," which are all formatted in an identical way to give the sentence a powerful, rhythmic impact, and to highlight the determination of the speaker.