the most difficult crochet technique?

Dear users, dear authors,
which crochet technique do you think is really difficult?

I find post double crochet pretty complicated—it’s not easy for me to get them off the hook.

Many people find it hard to crochet crab stitches because you’re working “backward.” Or wrap stitches, where you wrap the yarn around the hook multiple times and then have to work through those loops.

I also had a hard time with crab stitches at first. Since I crochet pretty tightly, it took me some practice to get a nice edge.

Crab stitches are my personal Waterloo. I’ve never managed to get them just right. And my inner perfectionist can’t stand it when an edge is uneven...
I like to work around these stitches by using twisted single crochets. They also make a nice, sturdy edge. :-) 

Twisted single crochets? How do you do them? I’m actually having a bit of a hard time with crab stitches, since they don’t always turn out quite even.
After crocheting a shawl with lots of post double crochets (front and back), they’re no longer a major problem. What often gives me trouble are treble or double treble crochets, since the last stitch ends up too loose.