NieR

Simply put, this is the time trial for the boss you face after the shadowlord to get ending C or D. Unfortunately it puts you in an annoying situation which takes careful preparation to avoid having to do extra playthroughs, miss key plot, or even worse consequences. This is long-winded, but if you don't follow the advised steps you may end up either seriously inconveninced or more likely completely and totally screwed.

I will avoid spoilers but give a procedure to get this achievement in the most efficient manner. On your ending B playthrough- ( when you are heading toward ending C or D), get as many key fragments as you can without doing the Aerie one. As you'll know by this playthrough, the Aerie will be destroyed after you do the key fragment quest there. That means you will not have access to the gathering points there for the rest of the current playthrough and the gathering point that is destroyed is the only place in the game to get eagle eggs and thus finish the achievement for upgrading every weapon to level 4. That means you want to make a save before you do that step. After that, just start saving your progress on a different slot and come back to that achievement later as it is the toughest one in the game by far and horribly time-consuming.

solution containing guide to obtain all the weapons:


Now, to do this without having to do extra playthroughs of part II, you'll want to have all weapons collected which allows you to choose ending C. If you finish this playthrough and have not collected all the weapons, your only choice is to take ending D which erases all your data completely.
With that said, when you have assembled all the key fragments and collected all the weapons, make sure to make a save at the mailbox on the roof of the Lost Temple just before you enter the Shadowlord's castle. This will save you a part 2 playthrough if you do this smoothly.

Proceed through the castle, defeat the Shadowlord, then you will face the boss you must beat for this timed achievement. What I recommend is that you do NOT go for this achievement on this try, because there are multiple cutscenes which you'll probably need to skip if you want to beat the clock as well as a lot of dialogue during the fight when I think the clock is ticking that is not skippable and you cannot damage the boss during the interchange. Skipping these cutscenes is especially sucky because they're basically the explanation, culmination, and conclusion of the plot of the game.

I recommend you watch the scenes, fight this final boss, and get used to its attacks- it jumps around a lot and its attacks hurt FAR more than any other enemy in the game. Even at level 40 on normal difficulty getting winged by this boss would take of a good chunk of health... for comparison the shadowlord took off less than a tenth of my health probably through the entire fight and getting hit by the ressurecting boar took off a couple pixels as another reference. I found the spear to be effective (I was using phoenix spear level 2) because the boss will leap around and shoot projectiles at you, and you can use the spears special lunge attack with the Y button and if you connect it will hurt the boss quite a bit and make it flinch at which point you can probably stab it once or twice with regular stabs before it leaps away. If ANY boss at all gave you trouble on your second/third playthrough I would recommend setting it on easy to fight this boss for the attempt when you go for the time trial here because comparatively the other bosses instantly die vs this one putting up a pretty solid fight.

After the boss is incapacitated, if you collected all the weapons as I instructed you will have the option to execute it. This will lead to ending C, which you should pick. Watch the credits, then at the ending save screen save in the third slot you DIDNT make your pre-Aerie save or your save from the roof of the lost temple. Exit the save screen and your ending C achievement will pop.

Now, load up your save from the roof of the Lost Temple and rush through the Shadowlord's castle again. You can skip all the scenes- they are exactly the same up to and including the shadowlord scenes and the pre-final battle against the final foe this achievement is for, as well as the cutscenes mid-fight agains the true final boss. This is where you want to make your speed run for this achievement. Skip all the scenes you can this time since you've seen them before, and when the true final boss is incapacitated and you regain control of your character, if you beat the clock, the achievement will pop right then- before you interact with the body. If you didn't win fast enough you're hosed and will have to reload your save from outside the castle and cut through the whole place again. Ugh.

If you managed to snag this achievement but still need to finish a couple other achievements, make sure you have backed up your saves on a separate memory unit and unplug that one from the system when you make this next choice just to be safe. If you did all this properly, go ahead and choose the sacrifice option instead of the execute option you get ending D, which intentionally has the effect of completely erasing all your data on the current memory unit plugged in to the system.

I know this was long-winded, but if you don't do it this way you will at best end up being inconvenienced with an extra playthrough or two of part 2 and/or missing major key plot. At worst, you could end up wiping all your data and be totally hosed if you didn't clean up all the other achievements beforehand and/or wanted to keep your saves. Now you can plug in your back-up save unit if that is the way you decided to do it, load up your pre-aerie save, and get to farming a stupid amount of materials, doing cultivation (not very hard, but a little annoying), fishing up "the fish" (easy), and getting 1million gold for man of means. Refer to the appropriate achievements if you want the low-down on how to get those done.