"Complete every career, classic, hawk-man, skill, film, photo, and line goal in the game with at least Pro ranking."You have to do exactly what is described in the solution posted on XboxAchievements, linked here:
https://www.xboxachievements.com/game/tony-hawks-proving-gro...This includes ALL of the progression-based missions (career, hardcore and rigger missions PLUS the 'impress SKATER' missions)
I can confirm you also need to do the races, as well as the high-score runs of each of the arcades. You will know when you've completed everything there is, besides the high-score runs, when you get the check for $900,000. (or was it 9 million?)
I suggest you limit your efforts of getting
SICK ranks for only those goals where they also unlock their respective achievements, i.e. the skill challenges, the photo, film and line goals, and the arcade machines (classic + hawk-man).
The in-game cheats do not void the achievement. They come in handy when you're doing the arcade machines. The cheats are listed below, emboldend and underlined for your convenience; enter them within the settings before starting them game.
STILLAINTFALLIN for
Perfect Manual BalanceAINTFALLIN for
Perfect Rail/Grind BalanceMYOPIC for
Infinte FocusSUPERSLASHIN for
Infinite Slash GrindsANDAINTFALLIN for
Bail Prevention