From the origins, the roman republic was defined in opposition to.

From the origins, the Roman Republic was defined in opposition to the Roman Empire or the Roman Democracy, the Roman republic had a very specific set of laws and rules which they used to rule the area. This was also the reason why they were so successful as a conquering force during their times.  

In my honest opinion , i’d say franklin d roosevelt was a president that impacted our nation , i say this because fdr is voted among top three best us presidents and he was the longest serving president by 3 terms , usually presidents only supposed to have two terms increments of 4 years , equivalent to 8 years total before election time. and he established the fdic , through the 1933 banking act and he established the us , social security system , during his presidency, and established a national minimum wage , through the fair labor standards act , fdr led the allied coalition to victory in wwii and he played a major role in the creation of the united nations.