function removeDuplicates() {
  var sheet = SpreadsheetApp.getActiveSheet();
  var rows = sheet.getLastRow();
  var firstColumn = sheet.getRange(2, 2, rows, 1).getValues();
  for (var i = rows; i >= 2; i--) {
    if (firstColumn[i-1][0] == firstColumn[i-2][0]) {
      sheet.deleteRow(i);
    }
  }
}

var firstColumn = sheet.getRange(2, 2, rows, 1).getValues();
  for (var i = rows; i >= 2; i--) {
    if (firstColumn[i-1][0] == firstColumn[i-2][0]) {
      sheet.deleteRow(i);

var firstColumn = sheet.getRange(1, 2, rows, 1).getValues();
firstColumn = firstColumn.map(function (e) {return e[0]})
  for (var i = rows; i >0; i--) {
    if (firstColumn.indexOf(firstColumn[i-1]) != i-1) {
      sheet.deleteRow(i);