The following eight AP's are considered some of the hardest available. Without extreme hard work and dedication, there is a very slim chance of passing the AP Exam. So, for all high-achieving students out there, these just might be your kind of AP's.
1. AP Chemistry
AP Chem is a particular hard AP due to the rigor of the course and the wide load of information, formulas and concepts you have to learn. Without knowing how exactly to use the information and formulas, it will be very hard to maintain a good grade on the class and pass the AP exam.
AP Physics
This difficulty of these AP Physics classes differs based on the school but the AP exam will be the same for everyone.
AP Biology
You can learn all the information from the textbook but without knowing how to apply the concepts, you will fail.
AP Computer Science
Like many other AP's, AP Computer Science requires you to understand how to code, where certain types of codes belong and actually apply it while coding using various soft wares. Although if you're planning on pursuing a career that heavily involves computer science, this might be a good option for you.
AP Calculus AB and BC
From what I heard from many people, AP Calculus ranks at the top three hardest AP's ever. Unless you're a mathematical genius. Some majors and colleges that you might be interested in might want require you to take the class so get ready if you're potential college wants you to take the course.
AP Literature
Unless you're extremely well versed, dedicated, hard-working and excellent at writing, this will not be an easy class for you. But if you're all of the above, go for it and you might even enjoy it.
AP US History
While the information might not be the hardest to learn, the work involved in the class will be hard to bear. If you're planning on taking this class, get ready for a flurry of essays, notes and Socratic seminars thrown at you on a regular basis.
AP French/Spanish/Chinese/German/Latin
Languages in general are extremely difficult to master. It's only logical that AP languages would be ten times harder, if not more. You will need to work extremely hard to learn the concepts, how to apply them and how to fluently speak the language besides just learning how to write and read it.