diffingAchievement.js

function getAchievements (dom) {
  return Array.prototype.map.call(dom.querySelectorAll('table.data div.Achievement'), function (a) {
    return a.classList.value.match(/Achievement_(\d+)/).shift();
  });
}

function removeOverlapping (ach1, ach2) {
  var table = document.querySelector('table.data');
  ach1.forEach(function (a) {
    if (ach2.indexOf(a) < 0) {
      return;
    }
    var el = table.getElementsByClassName(a);
    if (el.length < 1) {
      return;
    }
    el = el[0].parentNode.parentNode;
    el.parentNode.removeChild(el);
  });
}

jQuery
.get(document.location.href.replace(/\/\d+$/, ''))
.then(function (res) {
  var resDom = document.createElement('div');
  resDom.innerHTML = res.replace(/<script(.|\s)*?\/script>/ig, '');

  removeOverlapping(
    getAchievements(document),
    getAchievements(resDom));
});