Final answer:
Cato the Elder, a conservative senator, catalyzed Roman sentiment against Carthage which led to the Third Punic War.
Step-by-step explanation:
After the Second Punic War, the Roman individual who roused the Roman people to take action against Carthage again was Marcus Portius Cato, also known as Cato the Elder. He was not a military leader but a conservative senator who was known for ending every speech in the senate with the phrase "...and Carthage must be destroyed." This statement and his relentless advocacy for war led to the activation of Roman sentiment against Carthage, eventually resulting in the Third Punic War.
Learn more about Third Punic War instigator