Original :
This is more a tip than a solution, if like me you feel stuck in career mode (i was at around 70%) and they dont give you any new case to investigate.
Then continue to accept all random missions and once you have arrested almost 70 members of the syndicate, the story will continue.
On the main career menu when they show you progress bars, check the first one (how many syndicate members have been arrested etc ) the left side of the bar must be full and then the last chapter of the career unlocks.
Edit : According to comments below from Kugare and TangerineGamer, it's confirmed that you need to fill all bars to the mark to unlock the last case. Thx for their contribution.
Complete the last case and the achievement is your ;)
I hope this ll help you, i wish i knew it before, this would have save me a lot of time !