Blackwhip ability from My Hero Academia.
Keep in mind that settings may vary slightly between different versions. See below for more details.
When I tested this with different checkpoints and LoRAs, it seemed to work quite well.
Illustrious:
A LoRA weight of 0.9 works great, though you can adjust the strength as you prefer.
Prompts I usually used:
blackwhip, black and green energy, coiled around bod, green glow,