See Disliokes Fix

// ==UserScript==
// @name         Display dislike count
// @namespace    http://tampermonkey.net/
// @version      0.1
// @author       Anonymous
// @match        https://www.youtube.com/*
// @icon         https://www.google.com/s2/favicons?domain=youtube.com
// @grant        none
// ==/UserScript==

function format(number) {
    if (number < 1000)
        return number;
    if (number < 10000)
        return Math.floor(number/100)/10 + "k";
    return Math.floor(number/1000) + "k";
}

async function updateDislikes() {
    if (location.href.search(/v=[0-9a-zA-Z_-]{11}/)){
        let element = document.querySelector('#button[aria-label="Dislike this video"]');
        if (element) {
            element.parentElement.parentElement.querySelector("#text").textContent = "...";
        }
        let response = await fetch(location.href);
        let text = await response.text();
        let ratio = (text.match(/averageRating":([\d\.]*)/)[1] - 1) / 4;
        let likeCount = text.match(/label":"([\d,]*) likes/)[1];
        likeCount = likeCount.replace(/\D/g, '');
        let dislikeCount = likeCount / ratio - likeCount;
        let imageList = document.querySelectorAll('path[d="M17,4h-1H6.57C5.5,4,4.59,4.67,4.38,5.61l-1.34,6C2.77,12.85,3.82,14,5.23,14h4.23l-1.52,4.94C7.62,19.97,8.46,21,9.62,21 c0.58,0,1.14-0.24,1.52-0.65L17,14h4V4H17z M10.4,19.67C10.21,19.88,9.92,20,9.62,20c-0.26,0-0.5-0.11-0.63-0.3 c-0.07-0.1-0.15-0.26-0.09-0.47l1.52-4.94l0.4-1.29H9.46H5.23c-0.41,0-0.8-0.17-1.03-0.46c-0.12-0.15-0.25-0.4-0.18-0.72l1.34-6 C5.46,5.35,5.97,5,6.57,5H16v8.61L10.4,19.67z M20,13h-3V5h3V13z"]')

        if (imageList.length > 1){
        imageList[0].parentNode.parentNode.parentNode.parentNode.parentElement.parentElement.querySelector("#text").textContent = format(Math.round(dislikeCount));
        }
        else{
        document.querySelector('path[d="M18,4h3v10h-3V4z M5.23,14h4.23l-1.52,4.94C7.62,19.97,8.46,21,9.62,21c0.58,0,1.14-0.24,1.52-0.65L17,14V4H6.57 C5.5,4,4.59,4.67,4.38,5.61l-1.34,6C2.77,12.85,3.82,14,5.23,14z"]').parentNode.parentNode.parentNode.parentNode.parentElement.parentElement.querySelector("#text").textContent = format(Math.round(dislikeCount));
        }
    }
}

document.addEventListener("yt-navigate-finish", updateDislikes);
window.addEventListener("load", updateDislikes);
setInterval(updateDislikes, 3 * 60 * 1000);