Entity Framework - Start Over - Undo/Rollback All Migrations

For Entity Framework Core:

Update-Database -Migration:0
Remove-Migration

You can rollback to any migration by using:

Update-Database -TargetMigration:"MigrationName"

If you want to rollback all migrations you can use:

Update-Database -TargetMigration:0

or equivalent:

Update-Database -TargetMigration:$InitialDatabase 

In some cases you can also delete database and all migration classes.