My daughter, after having been hacked by me, multiple times, has come up with nearly unhackable passwords on her devices. The only way you'd crack her iPad is by videotaping her entering it. Something I haven't done yet.
I kid you not, her iPad password is at least 40 characters long. Good luck crackin' that!
My passwords, that matter, are all longer than 15 characters in mnemonics (mostly over 20). They mean something to me, but not to you. I don't do random hard to remember passwords. I do long, easy (for me) to remember mashups of words and word fragments of varying capitalization. Occasionally, I throw a random symbol in at a key location. I even mix languages. I read, write, and speak a dozen languages.
Some sites don't let me use my long hard to crack passwords.