WordPress Plugin: Autologin-Links
Generate url with autologin for every user. Go to the user profile and generate autologin-link. Then go to the page you want the user to come. Click in the top-bar on auto-login-link and select the user. A window appears from which you can copy the link.
For temporary logins (say you want to give a developer access to your site) use https://josvermeulen.com/snippet/temporary-login-without-password/