When you are looking for someone who is the "most" anything, it is often subjective -- that is, it depends on whom you are asking. Also, when doing an internet search (for example, on Google), you can get different answers depending on which search terms you use.
If you search "most notorious Canadian villain" you get lots of stories on Clifford Olson, Canada's most famous serial killer. He raped and murdered 11 victims in the 1980s. If you use slightly different terms, like "most notorious Canadian criminal" you may get more stories on Norman "Red" Ryan, a bank robber. I even tried just using "evil Canadian" and got a story about the "Evil reptilian kitten-eater from another planet," a term used to refer to Ontario Liberal Party leader Dalton McGuinty!
The internet has a wealth of information on it, for those who use it creatively. First, decide what is meant by "villain" -- what makes someone a villain? -- and try incorporating that into your search. Make a list of all the search terms you think would be helpful and try using them in different combinations.
Best of luck, and have fun with it!