Rocket League

To unlock this achievement, all you have to do is complete all 3 different trainings (saving, scoring and aerials) on any difficulty. However, you may be unlucky and have this glitch on you like it happened to me.

Fortunately, I found a workaround to unlock this, thanks to MustKillMoWhee's comment on the Team Player achievement (which is also glitchy). Note that there has been an update and, while this method still works, you will lose all your unlocked items and level. (Thank you ChingChongNolan for the updated info.)

I don't think it matters if you complete all trainings by selecting "change training" or if you go back to the main menu, but when I unlocked it, I did all 3 in a row using the "change training" option. Also, I don't think your percentage matters, I got 90%, 80% and 10% (yeah, I'm that bad with aerials haha), but I think you can get 0% every time and still get the achievement.

Now, onto the method itself:

1) Disconnect your Xbox from the Internet.
2) Go to your games & apps section, press the start button on Rocket League and select "Manage Game". Once in that menu, delete your local save file, (I also deleted the reserved space, just in case)
3) With your Xbox still offline, launch the game and complete the 3 training sessions as described above (you will be Level 1 and have no items). After completing the trainings, go back to the main menu and close the game.
4) Reconnect the Xbox to the Internet.
5) Open Rocket League. There will be a prompt asking you which save you want to use (console or cloud). Chose your Console save. The synchronization process will begin, and the achievement will unlock. After that, you can press A to load the main menu.


As mfeforever adds in the comments:

There seems to be a basic misunderstanding how game save and achievement data is split up and stored. The gamertag file contains achievement data. The game save file contains in game progress data (e.g., levels/unlock items.)
Following steps one through four, the achievement fired without ever starting Rocket League. (Be a little patient, when the gamertag synced back up. The offline gamertag had the achievement and needed to update the Xbox live gamertag. It happens fairly quickly, but not immediately.)
At this point, the achievement has fired.
In step five, the solution as presented resets the game save data, when the on console (recently created and mostly empty) game save file is selected.
Instead during step five, the Xbox live version of the game save file (the one with game progress data state prior to starting this workaround) should be selected. (Any xp/items you earned when offline will be lost, but the original state is restored.)
This was tested with my gamertag, which the achievement had been earned but did not fire, and with an alt gamertag, which had never started the game.
Hope this helps...


Since I already have the achievement, I couldn't test this, but it does make sense, so I thought I'd add it to the solution.

I think the "change training" method is outdated after update or something because it would not unlock for me. I completed aerial, hit exit to main menu on left side of screen, completed striker, exited to main menu, then did goalie and it popped.