In .NET EF core, Is it possible to remove/revert a Database migration after the database is updated by "Update-database" command?
Yes, it's possible, but only if it is the last migration or if you revert all migrations after it.
To revert all migrations including the desired, use the -Migration parameter of the same Update-Database command and pass the name/id of the migration before the desired (or special value 0 if it is the first)
Update-Database MigrationBeforeTheOneYouWantToRevert
For more info, see Applying Migrations - Command-line tools sections of the official EF Core documentation.