Federer's backhand used to be clear weakness in his early years at tour.
People pounced on it and improved a lot. Federer now has a great backhand.
I am not sure if I can call it as weapon that can frequently force an issue,
but great backhand.
Lots of 1 handers have weakness against lefties. It just one of the toughest shots in tennis.
For example, it's extremely hard to hit down the line 1 handed
backhand, from ad court, against heavily side/top spined lefty's forehand.