I did all specialist missions on all dificullty, i did all challenges, I had 30 stars. I repeat many times all missions, but achievement won't pop up. I tried to delete save file, I tried hard reset and everything that I know. I saw in TA site that I'm not the only one who can't unlock that. I found the reason for the glitch - When you complete all missions first time, you unlock the next dificullty and when you do the second dificultty, when you finish the first specialist, game automatically select the next character to the on regular - ok, but you have oppurtinuty to select the previous character and reapet the challenge in veteran. i think this is the reason for achievment to glitched.