The worst Mistake we ever made was eliminating taxes as a requirement to vote. (24th amendment.) Second worst was probably lowering the voting age to 18. (26th amendment)
The 14th amendment was also pretty bad because it gave the Courts infinite flexibility in manipulating real rights and real laws to suit their liberal preferences.
We made a lot of mistakes.
My wife says granting women the right to vote was a disaster for the Republic. Women in the aggregate vote for security for themselves and their children. Liberty is not terribly important. That said women should not be restricted from running for and occupying office. Those who get elected where no women vote will not be part of that “women in the aggregate.”
Worst was 19th imho.