I found a save on modio with lots of commands and one unlocked all achievements. So i made a profile called left4dead2 and tryed them, all worked + 1000gs so i hosted a game offline and did it for one of my profile as you can give the second profile the achievements. Wanted to do it today with my main profile but left4dead2 profile has 0gs the 1000gs has gone and checked on modio to see what button it was to unlock them but they do not say it anymore. DID I DREAM THIS ? HAS IT BEEN PATCHED ?. WILL I GET GS RESET DOING IT AS I DID IT TO MY MAIN PROFILE OFFLINE ON MY SECOND CONSOLE BUT DO NOT WANT TO TAKE IT ONLINE IF THEY GS RESET YOU........
You won't get your gamerscore reset because the command works by automatically firing off all the events needed to unlock achievements. So technically if you put your profile beside one that legitimately got the achievements there isn't any difference. If you're really worried about getting banned or something (which you won't), you can reset all your achievement progress and work for it legitimately using the achievement_reset_all command but I wouldn't advise doing so.