18年前有案底，攞唔到良民証，想搞團聚移民，可以在加拿大當地搞特赦嗎？謝謝各位解答?

I am not sure you understand the process.

In general, a criminal record will affect the chance of immigration. However, the exact impact depends on the record, i.e. the crime(s) that you have committed.

Canada allows rehabilitation, forgiving past criminal history:

https://www.canada.ca/en/immigration-refugees-citizenship/services/application/application-forms-guides/application-rehabilitation-inadmissible-persons-criminal-activity.html

The issue is not every record is eligible.

In this case, the best way to proceed is to apply this with Canadian Consulate for a non-binding decision to see your chance. If you have provided all details necessary, and Canada approves the application, there is no reason why you can't qualify for immigration to Canada because of your criminal history.