While all of these groups have historically faced challenges in gaining political participation, the group that gained more significant political participation through constitutional amendments is African Americans.
The 15th Amendment, ratified in 1870, granted African American men the right to vote. Furthermore, the civil rights movement led to the Voting Rights Act of 1965, which aimed to eliminate barriers to voting for African Americans.
Native Americans were not granted U.S. citizenship until 1924 with the Indian Citizenship Act, and while subsequent laws have improved their voting rights, they were not directly addressed by amendments to the Constitution. Asian Americans and Hispanic Americans also faced challenges but were not directly enfranchised by constitutional amendments in the same way.
So the best answer is African Americans.