Apollo is a surprisingly chill boss to do with no AC except one moment, but we'll get to it later.
The ceiling rubble wave can be easily destroyed by grounded up slash + air down slash as Apollo closes in on you. Honestly I think I might incorporate this into any potential S++ runs in the future, damage wise it's better than teleporting behind the boss. The same approach works for the move where Apollo does 3 half-screen trash ball summons. Keep in mind that just the up slash won't be enough (and it has to be stopped before the apex of Kirin's move) to destroy the hazards unlike the previously described attack and you will get hit.
As for Atom Smasher, this attack is fully doable as Kirin, it's just a matter of precise sword swings and wall jumps, and then you can do Issen to the corner of the room to dodge the big trash balls crushing you in the middle. I'll admit I haven't done enough experimenting with Issen on that part prior to doing this run, but hey, I did only ban AC, GV usage is perfectly fine, esp since merciless always has you build up enough meter for his summon before a boss can do their SP. That's why we use the same trick as Shiron's fight and abuse i-frames to dodge the trash crush.
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