This is the single most effective defense against credential stuffing. If you use a unique password for your Steam account, a combo list containing your details from a breach at, say, a food delivery app, will be useless against Steam.
Steam does not have a "Combo" button, but you can use these filters to build your own list: steam combo list
Games that have "Difficulty" achievements + "Speedrun" achievements. This is the single most effective defense against