How can use Anonymize IP address by Default and can see some visitors IP if needed?

Hi, I am reading on Piwik but not getting the sure answer. What I want to do is I want to use Anonymize IP feature, so privacy of user can be protected. But at the same time, if some user who needs to be block i.e from comment on site, I need to see his full IP address to block him. But since IP address is Anonymize in setting, so in this case how can I see IP address of user?

Thanks,

You can’t see IP if you enable Anonimisation of IP