Please read the manga again, carefully this time, I was talking about OUTPUTTNG RCT, totally different thing from Yuji or Gojo or Choso healing their own injuries. Did Sukuna heal Megumi by performing blood tranfusion? When Yuta kill that bug curse by kissing it, did he transferring his blood or positive CE?

Literally copied from JJK wiki:

"Reverse cursed technique turns cursed energy into Positive Energy (正せいのエネルギー Sei no Enerugī?) to regrow missing body parts and heal wounds. Cursed energy comes from negative emotions, unfit for healing living things. Reverse cursed technique uses the principle of multiplying a negative by another negative to produce a positive. While cursed energy flows from the gut, the brain directs reverse cursed technique. Positive energy can reproduce blood, bone, flesh, and organs, allowing proficient jujutsu sorcerers to recover entire limbs and withstand powerful attacks. The speed and effectiveness of this process are dependent on the user's cursed energy output. Reverse cursed technique can also remove toxins from a sorcerer's body and heal damage to their soul, though both of these skills are even more difficult than simple regeneration.

Reverse cursed technique is extremely complex and difficult for most jujutsu sorcerers to perform. One of the primary hurdles when using it is compensating for blood loss through a technical process that converts a massive amount of cursed energy into blood. Individuals who are naturally capable of doing this, namely the Cursed Womb: Death Paintings, can learn to use reverse cursed technique much easier than others and lack the drawback of large energy consumption upon employing it.

Most reverse cursed technique users can only heal themselves, as it is more efficient and less difficult to do than healing other people. One reason is the fundamental difference in application. Another is because the cursed energy of the healer and the receiver can be incompatible due to the latter's body rejecting the former's cursed energy or failing to respond to the conversion. Due to this, the effectiveness of healing other people is case-by-case. In the present day, only Shoko Ieiri, Yuta Okkotsu, and Sukuna are known to possess this skill."

https://jujutsu-kaisen.fandom.com/wiki/Reverse_Cursed_Technique