I’ll try the unsubscribe link, if that fails I’ll directly email addresses like contact@company.example, info@, support@, service@, hr@, admin@, abuse@ requesting I be removed from their mailing lists.

If all those fail (I’m still getting spam later), I whois lookup the domain and send a complaint the listed abuse address for the registrar. That typically goes through AWS who follows up asking for the email source headers to investigate.

It usually ends there.