A UI pattern I've noticed that has been increasingly common: Ask for the username, and only when that is submitted show the password field. Why it's bad: I use a password manager for all my logins which auto fills in username and pass. This setup requires twice the clicks
This can cause some confusion if a user who previously had a password switches to forced SSO or has multiple accounts. Still, should at most require clicking submit twice, password field should be populated once it appears.