If I just play the percentages against most of the lefties that I play regulary, I will lose every time.
However, if i intentionally hit every shot to their backhand and cheat towards my backhand, it will always be close. I may not win every match, but I have no chance if I just keep feeding their forehands.
There are 4 lefties in my league, and this is the case with 3 of them. The other guy has no power on his forehand so it doesn't apply. The other 3 can hurt you with their forehands, and will just keep pounding my backhand with more and more angle until I'm off the court. If I just take every shot and hit it to the deuce court (even weakly) until he runs around to his forehand, I'll be in every point, because even their best backhand is just a decent rally shot.
Of course, they try to do the same to me, avoiding my forehand at all costs, because it can do damage. It becomes a game of cat and mouse.
3.5 player. Equipment: Prince Original Graphite OS, Tourna Big Hitter Blue