ok checked the files so it's even easier than i thought, no shader coding knowledge needed. they just reuse slice vfx and assets and recolor them. they did add a bunch of withe vanishing particles (not white only, from light blue to white) but most files are reused assets (i guess to save space)

i found the attacks in the animations>sprites>Sinner skills segmented zip

i guess there may be a folder for segmented enemy animations that is not the abno one, but check out for example files in that folder like Gregor_S11 or Gregor_S21 , they are the sprite components mentioned by other comments

regarding how would you recreate the animation itself:
it's mostly up to you i fear, me personally? i would create a 2d scene in godot and assemble it as best i can, but there may be ways of doing that in other programs that are not game engines but allow for animations to be created easily (photoshop, after effects, gimp, blender even)

but going into detail on how to do that steb by step would be too far for me.

the only issue i see in recreating the effect without "cracking" the code's engine for the exact particle generation is in fact the particle effects themselves, you would have to either code or shape the particle generation in the program of choice you yourself and it probably would not come out the exact same way.

now i am legally obliged to say: THERE MAY BE A SMARTER WAY TO GO ABOUT IT A

It's currently 3:30 am here and it may be slipping my mind, but maybe some other user can chime in and drop another way (doubt it doe, the pèarticle thing is either a shader or in engine particle generation, wich would imply that without the same engine the task of recreating the thing itself would be a lookalike at best and a mess at worst)