The generally accepted hardest classes in pre-pharm are Organic Chemistry, Anatomy & Physiology, and Calculus. I might throw calculus-based Physics in there if the school you want to go to requires it.
Make sure YOU know what prereqs you need for the CoP you want to get into, that way you can gut-check whatever an advisor tells you.
Correct me if I'm wrong - isn't pharmacy in Canada a bacchelor degree then a post-grad degree? Are you looking at a pre-pharm prior to the bacchelor program, or are you talking about the bacchelor program itself?
Keep in mind that most of us are from the States, and the path to pharmacy differs in each country.