^ Are you saying you did a "virgin run" (no loss at any stage)? It was quite a while back I played this, but thought this impossible.
I did that once, yeah. It does involve hitting the "restart" button a bunch, though, so a bit of cheesing.
But even outside of that it really comes down to some RNG there as what skill you get from victory is not always the same thing for some reason, so one run might end up entirely different that way in a way that makes virgin run impossible. At that point you just have to start a new save.
But the way to best this game in general is to have as
few cards as possible (aside from permanent boost cards in some builds).
Ideally you want to create a deck where you get to use basically every single card you have almost
every turn. And exclusively use weapons with damage that ignores armor. The entire action economy largely changes in the players' favor once the enemy's "Defend" serves it no other purpose than to sometime eat up a stun grenade/stun gun in order to eliminate a more dangerous action hiding behind it.
Not having to care about the enemy's armor frees up a lot of candidate cards and SP that doesn't get used on it.
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Anyways, I just managed to do a
no-hit on the final boss (not virgin run)
Took a LONG time because you have hit "restart" in the lower right corner a whole bunch of times to not have the boss attack in the first round, or to at least have him have just one attack that is the first(or only) action when you have a flashbang, thereby giving a chance going forward since you'll have three rather than two points.
Deck composition:
Concentrate - 2
Stun Grenade - 4 (I've also done it with 3)
Neutralize - 3
Meditate - 4
Stimulant - 1
Attack Plus - 1
SP Plus - 1
The challenge is to last long enough without getting hit until you can make the SP self-sustaining while also deleting any Boss action. Like I said, a lot of restarts several times in a row like I was playing a Gacha game or something.
You basically have to get high enough to
always be able to use Meditate.
Frustratingly, I once got halfway with a slightly different combo before RNG had me get hit once. But with a slight tweak I got to this one.
One of the early gambling tricks depending on circumstance is to use Concentrate, hoping for Stimulant when you are otherwise not going to get hit that turn. Stimulant costs 0, so with luck that use of Concentrate can reap a bunch of extra points.
Honestly, the biggest stress factor was fearing I'd accidentally click on Stimulant too early while choosing what to use in my deck.
You want to take SP Plus generally as soon as possible, but you also want to make sure you'll be able to use Meditate on the next turn, so don't let yourself go to zero SP by choosing SP Plus.
I added Attack Plus just so the fight will go a bit faster. But I could only do one, as otherwise the RNG odds would force you to sit there the whole day tapping restart. It's also somewhat important to shorten the battle with Attack Plus due to the danger of freak RNG rendering you unable to remove an enemy Attack if you're playing long enough.
Once you're comfortably in the SP range where you're not at risk of being unable to use Meditate even after playing a whole hand, you want to make sure to always use Neutralize and Concentrate before Medidtate in order to spawn as many cards as possible. If you have run out of cards to draw and then use concentrate/neutralize, no new cards are drawn, thus making it wasteful when at that point you could just use Stimulant instead to reap more points from those cards.
But once you're at that point, your biggest challenge is simply to avoid accidentally using Stimulant too early, and then the RNG is overwhelmingly in your favor. You basically can't fail then so long as you mind your SP level.
Oh, but even if you're not interested in no-hit, this deck combo will otherwise win you the fight against the boss easily. If you have no concern about getting hit a bit then you can just pile on any "Attack Plus" you have to expedite it, and you can probably replace some of the Stun Grenades with Stun Gun instead if you have it.