Abyssal Suwako (Labyrinth of Touhou 2 Plus Disk)
Despite the Touhou Wiki's minimalistic description of this fight, Abyssal Suwako does have things going on under the hood. First of all, it's good to know that Abyssal Suwako has a static pattern:
Moriya's Iron Ring
Moriya's Iron Ring
Long-Arm and Long-Leg
Froggy Braves The Elements
Froggy Braves The Elements
Mishaguji-sama
Attack
Attack
Moriya's Iron Ring
Azure Arrow
Azure Arrow
Foggy Braves The Elements (end of loop)
...And that's it, that's the entire fight. Aside from Suwako's personal ability to target DEF and MND, there are no extra mechanics to worry about. It's weird that this fight is so simple because if 3peso really wanted to, they could have recreated Suwako's fight from Labyrinth of Touhou 1. Maybe they didn't because it was mechanically too similar to Mamizou? In LOT1, she could change between two movesets, with their own defenses, after a set number of turns... Though LOT2 Mamizou doesn't change her moveset.
Anyway, Suwako's four personal moves can be split into "ATK-based, single target attacks" and "MAG-based group hitting spells". For the first category, you have Moriya's Iron Ring (a single target PHYS attack capable of inflicting PAR) and Long-Arm and Long-Leg (a single target NTR attack with high damage but also high delay). For the second category, there is Froggy Braves the Elements (a group targeting CLD spell that can also debuff MND) and Mishaguji-sama (a group targeting NTR spell targeting DEF that also debuffs DEF).
Moriya's Iron Ring has +20 ACC, Long-Arm and Long-Leg has +24 ACC and Mishaguji-sama has +32 ACC. While only Froggy has no ACC boost, you probably shouldn't expect a consistent performance from evasive characters here. Her other attacks (generic Attack and Azure Arrow) are not as impressive as Suwako's skills though they can target slots 3 and 4.
Suwako resists most ailments, but is slightly less resistant to TRR and SIL. She strongly resists NTR, and resists FIR, CLD and DRK, but is weak to MYS, SPI, WND and PHYS. I looked up the stats for Abyssal Suwako; while Abyssal Suwako has no entry, her Heavenly version does and if it's accurate, then she has slightly lower WND and MYS resistance. She also shares her Heavenly counterpart's weakness to DTH. Relevant video:
...I've written all of this but Abyssal Suwako honestly isn't that impressive. The group hitting part of her static loop is scary: Froggy Braves the Elements has a relatively short delay despite its damage, so it can really soften up your front row. And Mishaguji will annihilate anybody not built to tank it. But Suwako is mostly stuck with single targets for the rest of her loop so she's easy to overwhelm.
Her weakness to MYS is also extremely abusable. For example, my Marisa can do 50% of her HP without even maxing out her Custom Mode passive. That's an extreme example but Suwako's glass cannon stats and her weakness to MYS makes her a sitting duck to a LOT of magical attackers. Utsuho, Iku, Mamizou and Yuuka could all stick to normal Attack and probably do fine. All you need to be aware of is Suwako's somewhat high EVA.
Music is "Native Faith" from Touhou 10
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