To make Animated Slash Effects, you would need Blender, Photopea, a website, and a free Sprite Sheet Maker(a website online).
Here I created a youtube video to guide on how to make animated slash effects.
Overall Steps:
Create a mesh with simple deform to make the circular shape of a slash.
Add shaders with voronoi texture and gradient texture.
Animate markers position in color ramps connected to each texture.
Render every frame with png output format and background being completely black.
Add all the pictures to the sprite sheet maker.
Make sure to make the data type CSS and padding size 0.
Use photopea to remove all the black color on the sprite sheet.
Enable Flipbook particle system in roblox studio under beta features in file.
Add the sprite sheet to particle system texture and set the flipbook to 4x4.
Make the flipbook oneshot type.
There you go!
SpriteSheetMaker: Free Sprite Sheet Packer - A free alternative to TexturePacker
Photopea: https://www.photopea.com/