DakiNezu

"Why is the Leg I chopped off piercing my back? You regenerated it instantaneously? No way! That would make your regenerative powers... Greater than mine!"

- who said it

DakiNezu is the Femslash ship between Daki and Nezuko Kamado from the Demon Slayer fandom

Canon
Nezuko and Daki were always enemies and never had a close relationship, proven when first interaction, on Episode 39 of the series, as well as the 13th episode of Demon Slayer's 2nd season resulted in bloodshed as Nezuko struck Daki with a powerful kick, obliterating the latter's head to defend her brother. She was also further angered when she discovered all the innocent humans Daki brutally murdered.

From that point the two female Demons continued to batter and mutilate each other as once Daki realized that Nezuko was a demon wanted by Muzan she stated that she would gladly defeat Nezuko for him, who tried to attack her again, only to have her leg severed, it didn't stop there as Daki used her Obi to severely lacerate Nezuko's body, severing her arm and practically dividing her body before throwing her into a building.

Nezuko was badly injured trapped in rubble by the last attack and Daki laments about how weak she is and suggests she doesn't move, Daki simply states that since both her and Nezuko are Demons she won't "bully" her anymore and decides that as she'll absorb Nezuko into her belt and allow the sunlight to kill her. As she pulls out her sashes she berates about how pointless it is for Demons to have to kill each other.

After she finished, Nezuko not only broke free from the rubble but regenerated her leg, Daki was in question as she was positive her attack severed Nezuko's body. Nezuko then regenerates her arm, shortly after and that's when Daki realized that her opponent's regeneration is on the same level as Upper Rank Demons.

Nezuko transforms with her body having grown in size and her muzzle extracted and turns to Daki. She swiftly charges at her with another kick but Daki slices her arm and leg off, mocking her using the same attack pattern and threatens to slice her next off. But Daki was pierced and suddenly forced to the ground by Nezuko, despite having amputated her.

Daki was in shock, because she was pierced by the leg, she had just chopped off moments ago, contemplating rather Nezuko regenerated it in an instant, realizing if that were true than Nezuko's regenerative abilities would outclass her own.

Nezuko further injured Daki by stomping her arm off, putting Daki in further pain, Nezuko sadistically smiled having enjoyed Daki's pain. She followed up by stomping her other arm breaking it and prompting Daki to scream in pain, as Nezuko mercilessly continues stepping on her over and over until Daki retaliates by chopping off her leg and neck.

Daki quickly gains distance and opts to chop Nezuko into pieces, amputating her further, however Nezuko manages to stop her sashes by congealing her blood and after Daki caught on she was set ablaze by Nezuko's Blood Demon Art and was being burned alive, reminding her of a traumatic event that happened when she was human. Nezuko reattaches her limbs and appears delighted at Daki's torment as she leaps in the air as her Blood Demon Art finishes incinerating Daki, she forces Daki's head into ground, who recovers from the attack and resurface, with her face as well as other parts of her body being severely burnt. Nezuko forces Daki's face back into earth repeatedly and kicks her down the road before chasing her down with hurtling speed and follows with another powerful kick, forcing Daki through several houses.

Nezuko and Daki's battle come to an end when Nezuko tried to attack a wounded bystander but her brother managed to stop her, he managed to get her back into her senses by singing a lullaby that her mother use to sing her when she was young, and Daki was decapitated by the Sound Hashira and forced to release her brother to back her up.

However, Daki does mention to her brother that Nezuko burned her and asks if her brother can kill her and also mentions that he was ganged up on and "bullied" even those two statements were false.