This is an annoying achievement. A 50 game streak without losing takes a lot of patience and focus. A single loss will ruin your streak and potentially waste many hours of gameplay.
However, semi-professional difficulty is fairly easy, even if you are not an great FIFA player. I suggest playing manager mode with a good team (I used Inter Milan) and aim to go 2 goals up early in the game. This way you are fairly safe until the end of the game.
You should also see the
Winning Streak achievement. As you will have to win 60 games in a row for that achievement, it is recommended that you do not settle for a tie whilst going for this achievement. Aim to win every game along the way.
Please either comment below or send me a Personal Message if you have any comments or improvements.