I'd like to know all the ways to auto-crit. The only ways I know are through the paralyzed and unconscious conditions, and the Assassin rogue's Assassinate ability.
The only ways I know to impose the paralyzed condition is through the spells hold person and hold monster; and the unconscious condition through the spells sleep, eyebite L6 (can cause sleep), and symbol L7 (can cause sleep).
And, possibly the command spell to cause sleep for 1 turn if the DM allows it.
So for doing this somewhat reliably and not being over level 10, boils down to sleep, and hold person/hold monster.
What's the comprehensive list of ways to auto-crit in D&D 5e?