I've already tried all ...

Get-Mailbox -Database "Database"
Get-Mailbox -Database "Database" -Archive
Get-Mailbox -Database "Database" -Arbitration
Get-Mailbox -Database "Database" -PublicFolder

even cleaned up everything in this database with already deleted mailboxes with retention period. It is completely empty and in can not be deleted because of error

"This mailbox database contains one or more mailboxes, mailbox plans, archive mailboxes, public folder mailboxes or arbitration mailboxes. To get a list of all mailboxes in this database, run the command Get-Mailbox -Database <Database ID>. To get a list of all mailbox plans in this database, run the command Get-MailboxPlan. To get a list of archive mailboxes in this database, run the command Get-Mailbox -Database <Database ID> -Archive. To get a list of all public folder mailboxes in this database, run the command Get-Mailbox -Database <Database ID> -PublicFolder. To get a list of all arbitration mailboxes in this database, run the command Get-Mailbox -Database <Database ID> -Arbitration. To disable a non-arbitration mailbox so that you can delete the mailbox database, run the command Disable-Mailbox <Mailbox ID>. To disable an archive mailbox so you can delete the mailbox database, run the command Disable-Mailbox <Mailbox ID> -Archive. To disable a public folder mailbox so that you can delete the mailbox database, run the command Disable-Mailbox <Mailbox ID> -PublicFolder. Arbitration mailboxes should be moved to another server; to do this, run the command New-MoveRequest <parameters>. If this is the last server in the organization, run the command Disable-Mailbox <Mailbox ID> -Arbitration -DisableLastArbitrationMailboxAllowed to disable the arbitration mailbox. Mailbox plans should be moved to another server; to do this, run the command Set-MailboxPlan <MailboxPlan ID> -Database <Database ID>."

Database was once corrupted and repaired. After that i moved all mailboxes from it, but it just cant be deleted. Is there a way to force delete or manually clean it

already found solution.

1 ) Get-MailboxStatistics -Database DATABASE | fl DisplayName,MailboxGuid,Database,DisconnectReason

show me that there is archive mailbox of user in the database (it was not visible on other GET- commands). Archive was disabled via GUI earlier (so i was sure it was ...). Some kind of bug, maybe ...

2) Disable-mailbox USER -archive       

did the trick, so

3) Remove-StoreMailbox -Database DATABASE -Identity "GUID of mailbox" -MailboxState Disabled

Killed that remaining trash. Guid can be found via command 1.