Originally Posted by CL1333
Can I know that did you unlock the Act 1's Killer difficulty's achievement? I believe mine was glitched and didn't able to unlock it...(Act2-9 were fine). Even I open a new game to play Act 1 on Killer Difficulty this couldn't unlock ...OMG. My next step will be delete save and open a new play through to give it a try...
It's probably never going to unlock for you, people have had some strange glitches which they never found a way around on this game. Examples:
No achievements for a certain act, but got all others.
No achievements for 10 curved bullet kills, but got the one for 10, etc.
And yes, my killer achievement unlocked.