I'm not sure if this qualifies as 'ridiculous lengths', but one of the hardest
and most time-consuming achievements I've ever gotten is the
Knight's Honor achievement in
Dark Souls: Prepare to Die Edition. It requires you to collect every unique weapon and shield available in the game with one character. That includes boss weapons you can only acquire by trading a particular boss soul for it, and items that are locked behind a particular covenant.
It took me hours of farming and playing through the game three times with the same character to collect all of it. One of the boss souls, namely that of the
Great Grey Wolf Sif, is required for two different swords and a shield! That means you have to beat New Game+ and beat him on NG+2 before you can collect all of the weapons, and then you also have to play up to Anor Londo on that game cycle before you can actually transpose the soul into the required weapon or shield.
I actually remember finally getting there, fired up to collect the last weapon I needed before the achievement would pop. In my excitement, I accidentally bought the wrong weapon! Upon realising my mistake, I panicked
hard. I figured I would have to do another entire playthrough to get it, after I had already struggled to get here for some 60+ hours. I quickly Alt+F4'd out of the game and halle-flippin'-lujah, the game had not autosaved yet. I was standing outside the door to Anor Londo cathedral, boss soul still in hand. When I traded it for the right weapon this time, the achievement finally popped! Whew!
I went on to collect ALL of the achievements for Dark Souls, and I'm very proud that I managed it, but Knight's Honor was the hardest part by far.