Wilson Kill All the Things spray will do it.
https://www.rona.ca/en/product/wilso...203060-1298201
I had some behind my garage alley side, and have eradicated it. Probably 3-4 treatments, I did mix as directed into a spray bottle. Note that it will kill everything(which is why I labelled my spray bottle that way), so you need to target the leaves, or brush it on. I didn't care much in my alley about the other weeds I'd be killing. Re-apply in a month or so when you see the strugglers trying to make a comeback.
Don't listen to the garden people who say nothing gets rid of it, they are usually talking natural methods. Nothing is unkillable.