Defeating Arachnero:
The Shield-Killchain Strategy
Yes, you pretty much know this one already based on what you've read.
If you have a weapon that is fast and powerful enough, you can destroy the shield so fast that the Phalanxpheres will continuously reform the shield while you destroy it again to increase your killchain and thus the feedback loop escalates.
There is always a chance that a Phalanxphere will instantly decide to home in on Vincent, thus quitting any shield reformation and making it impossible to add to your killchain (unless Meteor Bullets are currently falling towards you). Using cheats I was able to instantly defeat the shield with one shot when it reformed, but when I got to killchain 55 randomness decided that a Phalanxphere would start targetting Vincent and so the cycle ended right there, even with cheats.
The slower and weaker your weapon the more you'll need randomness to delay the Phalanxpheres targetting Vincent in order to get a chance to destroy the shield enough times for a great killchain. That's why this strategy is only really recommended with the Ultima Weapon, even though it is sort of viable with the Powered Cerberus.
Fun facts: The Japanese guide book, "
DIRGE of CERBERUS - FINAL FANTASY VII - OFFICIAL COMPLETE GUIDE", never goes over many fine details of this boss battle like for example the three-leg defeat condition for Arachnero. It does however on page 215 recommend the shield-killchain strategy for this boss battle.
Transcriptions:
実際にアルテマウェポンを使ってみよう
アルテマウェポンを使えば、ボスも楽に倒すことがで
きる。ここではネロ・ラフレアを例にアルテマウェポンだ
からこそできる攻略方法を紹介しよう。まず、アルテマ
ウェポンにマスターMバレルとパワーブースターγorβ
を付けた状態で、ネロ・ラフレアに張られたバリアを攻
撃する。すると通常ではなかなか壊れないバリアも簡単
に壊せるのだ。しかも、バリアを壊すと子機がバリアを
張るためにこちらへの攻撃を中断するので、敵に反撃す
る機会を与えずにボスを倒せる。高いPOWとSPDを
持つアルテマウェポンならではの攻略法といえるだろう。
バリアを壊しつづければチェインゲージを溜
めることもできる。攻撃力が上昇すれば、
バリアを一撃で破壊することも可能だ。
Google translate:
Let's actually use the Ultima Weapon
If you use the Ultima Weapon, you can easily defeat the boss.
Here, we will introduce the strategic method that can be achieved only with Ultima Weapon,
using Nero Rafurea as an example. First, with the Master M Barrel and
the Power Booster γ or β attached to the Ultima Weapon,
attack the barrier put on Nero Rafurea. Then you can easily break barriers that usually
do not break easily. Moreover, if you break the barrier, the slave
will stop attacking you in order to put a barrier, so you can defeat the boss
without giving the enemy a chance to fight back. It can be said
that it is a unique strategy of Ultima Weapon with high POW and SPD.
The chain gauge can also be accumulated if the barrier is broken.
If the attack power rises,
it is possible to destroy the barrier with a single blow.
Arachnero, or "Nero Rafurea", as seen on page 213: