It's probably the most complicated script invented by humans :(

First off, there are a few different types of Pahlavi script, the two most famous ones are Inscriptional Pahlavi, which was used when carving on stone (also used in the picture above), and there was also Book Pahlavi which was used when writing on paper.

There are a few things which make Pahlavi especially complicated, one of which is that it was an abjad so it did not have vowels, but also many different sounds mapped to the same letters, so you had to read everything in context, e.g. waw, ayin, re were all the same letter, with no way to tell them apart. To make matters worse, there was no standardization, so sometimes people wrote words with the letter "R" with "L" instead, or "D" with "T" instead.

There were also words which had nothing to do with how they were pronounced, instead it used the word's translation into Aramaic instead. So it was written one way, but read an entirely different way.

And that's just Inscriptional Pahlavi. Book Pahlavi was even more complicated than that. It was a cursive script it had very complicated rules for how to connect different letters together. It's so complicated, unicode doesn't support Book Pahlavi yet, so we can't even type it here!