Answer:
I will assume you mean the United States Constitution. As an added bonus, I will give you three of the worst changes (in my opinion).
The 16th Amendment introduced the federal income tax.
The 17th Amendment changed the election of US Senators to a popular vote. They had been chosen by the method chosen by the state legislatures (usually through the votes of the state legislature).
The 24th Amendment abolished the poll tax thus supposedly making voting more fair, but in reality allowing an easier path to election fraud.
Amendment 16 - Status of Income Tax Clarified. Ratified 2/3/1913.
The Congress shall have power to lay and collect taxes on incomes, from whatever source derived, without apportionment among the several States, and without regard to any census or enumeration.
Amendment 17 - Senators Elected by Popular Vote. Ratified 4/8/1913.
The Senate of the United States shall be composed of two Senators from each State, elected by the people thereof, for six years; and each Senator shall have one vote. The electors in each State shall have the qualifications requisite for electors of the most numerous branch of the State legislatures.
When vacancies happen in the representation of any State in the Senate, the executive authority of such State shall issue writs of election to fill such vacancies: Provided, That the legislature of any State may empower the executive thereof to make temporary appointments until the people fill the vacancies by election as the legislature may direct.
This amendment shall not be so construed as to affect the election or term of any Senator chosen before it becomes valid as part of the Constitution.
Amendment 24 - Poll Tax Barred. Ratified 1/23/1964. History
1. The right of citizens of the United States to vote in any primary or other election for President or Vice President, for electors for President or Vice President, or for Senator or Representative in Congress, shall not be denied or abridged by the United States or any State by reason of failure to pay any poll tax or other tax.
2. The Congress shall have power to enforce this article by appropriate legislation.