The 16th and 17th Amendments, both ratified in 1913, are the ones that have corroded the Republic, IMO.
I'd like to see three Amendments ratified:
1. The sixteenth article of amendment to the US Constitution is repealed.
2. The seventeenth article of amendment to the US Constitution is repealed.
3. The powers not delegated to the United States by the Constitution, nor forbidden by it to the States, are reserved to the States respectively, or to the people.
I've not given much thought to the 17th Amendment, but #16 touches a nerve, especially the Federal Income Tax, and the establishment of the Federal Reserve.
I'm not a big fan of the Fourteenth Amendment either, because these days it's being exploited as the "anchor baby" law.