Just got the full completionist the other day. YES!
I didn't find it as challenging as I thought except for a few of the achievements. That one where you need to 'kill all enemy ground targets with the rods without harming allies' (or whatever it was) was probably the hardest for me, mainly because the checkpoint to restart the section was either at the point where you have to restart the ENTIRE mission, or juuuuussst make the 'restart checkpoint' button.
Extinction is my game mode in Ghosts. I love it compared to the everything else, so when I did the achievements I didn't find them as hard as I thought they would be. I do admit that when I first started Extinction, getting a completionist was a daunting task, but they were in the old days haha.
One thing I was a bit disappointed with was that there weren't many Squads achievements, there should have been one, for say, getting a round 50 or so on the wave mode (forgot its name sorry).
Anyway, 2000 club! Woop Woop!
Just completed them on the 360 now for the 4000. Still need to help some friends wrap some Extinction ones up now.
Some games I can complete in a weekend. Others a week. The original Titanfall achievements took me a month. CoD co-op modes are no joke. They are very challenging and take teamwork.
There were multiple times I was completely burnt out of Extinction before I got the completeionist. I found them difficult. But not as difficult as spending 7 hrs straight with a friend unlocking the Origins ee.
Wonder what AW has in store...........