Soak it good with Penetrating Spray..... vise grips dont work good!
Go buy the small Channel Lock Nut Buster pliers.... they will get it off way better and
they wont lose grip... they'll snap the head off before they slip!
https://www.all-spec.com/products/410.html
Since you are in Quebec... Cndn Tire sells them :-) and I believe they are even onsale this week :-)