This can only be done in Chapter 4 - "Saint Mihiel"All three final attempts must be done perfectly, though they can be done out of sequence. It only says the third time because this is literally the third time she has saved his life.
ALL THREE FINAL SEQUENCES. DOES NOT HAVE TO BE ALL AT ONCE. You can do the third perfectly, then go back and do the first two, for example.
First off anyone playing on an HD 42" TV or higher like me probably isn't very easy because everything is faster and your eyes can't adjust to the screen. So what I suggest is to play on a smaller TV or Computer screen though you'll have to start over but just go through it play the level again and come back to this point you don't need to do the first two parts again perfectly, it saves it from before if you did it perfectly. This should make it slightly smaller you'll have to get use to the new screen for awhile.
If you don't have a smaller TV than just keep trying it on your normal TV. The snap feature worked best for this part but Xbox updated to no more snap.
Mute the sound. Make sure noise isn't affecting you. Close your door if you have to or go in a quite room. (Pause your game if needed to know whats next. Keep practicing the buttons for your memory to get use to the sequences.
If you miss or hit the button at the wrong time just mash buttons together that will kill/bleed out Karl so you don't have to redo the whole mission just the sequence again.
This is for the last part of the phase at the end after the med pack, this has to be done flawlessly as well as the others before this part:
Sequence 1 - A X X Y....A X X Y....A X X Y....A X X Y+B
Sequence 2 - A A A A A A A....X X X X X X...A A A A A A
Sequence 3 - A X X...Y B B...A X X...Y B B...A X X...Y B B...A X X...Y B B...A A A A A A...X X X...A+X
(Repeating sequence gradually gets faster and the final A's and X's slow the pace back down, kinda tricky there)
Just be patience don't stress about this achievement if you have to come back later for it or get a good nights rest. I know it's a pain I play on expert guitar on Guitar Hero and it's not very easy but doing it more and more makes you better to where you can do it. Don't give up!DON'T FORGET COMPLETING GAME ACHIEVEMENT POPS AT THE END OF THE CREDITS WATCH THEM!
Congratz to people that beat this, is one tough cookie.