In our games, killing a high level character with a single scroll is a way of saying "Really? Did you even try to think things through". This is because: 1) spell turning 2) your spells tend to be much higher CL than castings from a scroll, and the defensive capabilities of appropriate enemies reflect this 3) scrolls are incredibly cheap. You should expect any enemy you fight, even a 'measly' level 5 bandit to have access to any scroll in the game if need be, with the possible exception of spells with large material component costs (like wish). 4) We generally expect high level players to have a great deal of defenses specifically set up to protect against Wishes, Miracles, and the like. There's hardly any point in creating a dedicated plane of existence in accelerated time continually monitoring you for Wish-related shenanigans if you haven't even protected against something like dominate monster yet (which is mind affecting, so, REALLY???).
Nonetheless, just having the right spell is often the right solution, and you asked specifically how to get him to fail this save. If it's got to be this spell and its got to be from scrolls, I suggest having someone learn the spell (if necessary) and start an exponentially growing crafting system producing it. You need to out-produce his luckblade generators, which you can do, given enough time, but he likely has a large head-start on you, and this could take a long time. The biggest contributing factor to your success here is that while you can just hire or produce an army of patsies to try and use the scrolls for you all at once, he has to have all of the luckblades in his own personal possession. He may have been content with a few million fine-3 luckblades in a bag or as a shirt or something (I know I've been guilty of this before), in which case you should be able to overwhelm him easily. Even if he does have a immediate-action distribution system set up, it's DEFINITELY more expensive than your scroll and almost certainly takes longer to produce. You're fighting a Magus, which means he doesn't normally have access to certain crafting-time lowering wizard discoveries, but his crafting system might.
If necessary, while running your own exponential crafting system, track down some of his crafting planes and unleash an exponentially growing army to subvert and destroy them. You'll probably get some loot and besides, it's the kind of dungeon crawl high level play is all about.
In any case, once you have 400+ times as many scrolls as he has luckblades, you and your fine-sized army should go ambush him and cast that spell a few milliatillion times. Remember that most of your minions only successfully cast the spell on a 20, and may need boosters even then, and that he probably only fails on a nat 1. This should work, but these sort of shenanigans should probably have been going on since at least level 10, so YMMV if the GM decides you are 'too powerful'.