In FM 15? Toni Kroos.
Bought him bunch of times and had few Real saves. Every time he is absolute garbage. In my most recent save I ended up benching Kroos, and playing 17 year old Ruben Neves with 120 CA and 5-7 points below in all the key stats for the role (DLP-S) and he's actually performing significantly better. Better pass accuracy, more key passes, more goals, game rates him 7.1 points on average, compared to 6.6 for Kroos.
I don't know what the **** is up with that. I peeked in the editor and even the hidden stats point out that Kroos should be godlike, but he's simply ****.
Using Kroos at DM or CM? Guess he'll be perfect as an APM in an attacking role at CM..
He's rated among the best cm's on my game going into 2020 now!