It's not that bad, around 4-6 imo. Straight ball his low shots, it goes over. Low parry is your friend up close. A good footsie tool against him I found to be air ball.
A lot of the time I feel LK players get caught by low parry because they don't know the match up. I've played some LK players more familiar with Commando who mix up their pokes to make parrying less of a read and more of a guess. As for straight ball and air ball, it's still in LK's favour full screen as a blocked low shot isn't punishable, but a blocked ball/air ball will cost you dearly. A good player will fire low shots to bait a ball and block it.
I agree it's not unwinnable, but I feel that all three LK's have the edge over Commando. Cyber can make things difficult full screen, and Cutthroat can be horrible in the corner, but even then LK's tools are better. Defending against LK is harder than defending against Kano. You mostly block low for both, but Kano needs to be right on top of you for his overhead to hit, where as LK doesn't have that problem and can nibble away at your health with a few well placed ones.