Thank you for the help, but first let tell you what I tried to do before you replied.
I decided to try ME3 and noticed when creating a new game I was missing several ME2 Achievements affecting the ME3 progress. So I went back to ME2 and tried something else.
While the cloud sync being disabled, I loaded a new game in ME2 from one of the existing working careers ( with only two save files, autosave and chapter save) the game at the beginning. What seemed odd to me that I had the credits & minerals for having accomplished the game once including the weapons acquired in the first run but my Achievements and medals list was entirely not achieved including the reach lvl 30 with one character. I am already lvl 30 in this new game with 51 distributed points. But have no achievement regarding these facts or any others. So definitely it is a career/character file issue and not a save file problem.
On the other hand I checked my saves folder and couldn't find any folder matching the current last saves. In this newly created game I had 8 new saves that did not appear in any of the existing save folders located in Documents\BioWare\Mass Effect 2\Save.
I could see a different load screen board and loading nonexistent saved files as if these saves were temporally saved in a different place. So I saved my game and quit, then I turned on the cloud sync, and started the game again and resumed where I left minutes before, I checked my save folder again and it was then when the new save folder was created/updated. So now, after the sync, there is a folder corresponding to the new game saves that matches the saves I see in the game.
I did something more, I added the old save file, the one with the most advanced career, to this folder and opened my load screen and it was there, I managed to load and resume the game at the point I was before all these trouble started. Now I have all the team and loyalties missions accomplished but if I check the Achievements, I find that all the loyalties achievement and many more still missing.
So even in the game load with the old save, I have all the weapons, Paragon and renegade went high but still missing all the achievements. I have just few ones, the achievements acquired in this new campaign.
In each save character folder there is ChapterSave file. I assumed it was the character profile/career of each new campaign. I switched across the files from the old save to the new save to check whether the accomplishments are reestablished but nothing changed neither.
Finally I did the steps you asked me and moved out all the files except the auto save and went adding the save to the folder in portions and i did manage to load but with the same result, no achievement history.
Any other suggestion?
