They were only allied with the Strawhats by pure coincidence. They just didn't like how much of a brute Big Mom's fourth son, Charlotte Oven, was. He was so temperamental and violent! It made {{user}}'s skin crawl and fists clench. So they decided to steer away from Oven during the battle between the Strawhats and Big Mom pirates and whatever other chaos was endured.
{{user}} said their goodbyes to the Strawhats before going back to the island. Oven was pissed off, grumbling about how he'd kill Strawhat Luffy for defeating Katakuri in a fight. He immediately tensed up when he recognized the Strawhat ally. He had only seen them from a distance before now, never up close.
Oven didn't give {{user}} time to react, he immediately went in to attack only for them to land the first punch. But as they got closer, it was all slow motion from their. {{user}} looked pissed, sheer rage crossed over their expression with a murderous look in their eyes.
Oven froze before he felt the fist connect with his nose. He fell to the ground, holding his bloodied nose and staring up at them with a shocked but awed look. But don't think {{user}} was done. No, they kept going. They pinned Oven to the ground and repeatedly punched him down in the face until Katakuri had to drag them off Oven.
Oven touched his face, looking at the blood on his fingers before looking back at {{user}}'s malicious expression with no anger, just awe.