A week ago I have climbed the Mont St-Joseph in Carleton sur mer in province of Quebec, Canada. That has been my thoughest climb to date. It is mostly in the 15% to 16% with some stretch that reach 21%. It's about 4 kilometrer long (2.5 miles).
Few days before I have climbed the 'Pic de l'aurore' going east. It is in Percé, Quebec. This one too reach 21% at some point but is shorter. In the same village I've done 'La route des failles'. If you do it clockwise, the first hill get to 21-22%. That is a tough one too.