Invincible not unlocking

[normanji]

hi, i've done the game 3 times now and the achievements hasnt unlocked.
i've done it on easy and got all weapon achievements.
so went through again on easy till last checkpoint, saved then return to hq, changed to formidable backed to hq so it saves then back to title screen then gone to continue last check point and finished level on hard, i then changed back to easy and carry on. should i at this point back out to title or am i ok to change to easy then carry on?

[Xenolith666]

I see the strategy for this is posted right below yours.. maybe you should read that. I just unlocked Invincible by just playing the levels on the same campaign save. Just change the difficulty to Formidable. With max upgrades and using War Machine with 2 mini guns as primary and 2 missile launchers as a backup you should run through the game without issue. Maybe you should try that.. only took 2-3 hours to finish the game.

[normanji]

yeah im doing the guide that is below my post, but its not unlocking. gonna give it one more run though.

[normanji]

achievements popped after doing lvl5 must of missed it somehow.