yes you can get banned for it i got banned for modding my achievements so dont mod your achievements

No you mod all your games just do one at a time that means no ban

If you mod your achievements you won't get banned, your gamerscore will get reset IF you get caught. If you are modding a game with a gamesave OFFLINE (for example CoD WaW Campaign, you'll be fine. If you are doing it ONLINE (for example CoD WaW Nazi Zombies), you will not get banned unless enough people (normally ALOT, about 20-80 people) file complaint you. So NO, you will NOT get banned.

mod only games offline

OnlineGangster wrote I was wondering if you can get banned for using game save to unlock achievements?

i think thats a yes because then it is modding your achievements ?
if you do it more than once after they reset your gamerscore then yes most probably

Any form of modding could possibly result in a ban. There is no such thing as a 100% safe mod. When you mod anything, you face the chance of being banned.

yes there is always a chance getting banned by doing MOD
"safest way is just get at least 1-3 achievements a day/week (still NOT 100% safe)"
that should do the Trick for not getting banned cause if you unlock 10 achievement at once i think Microsoft can detect the Time/Date of that achievements.

this is the ultimate facepalm question