


I Think Some People Misunderstand How Mahito's Technique Works
I see an astonishingly large amount of people saying stuff along the lines of "you need soul damage to kill Mahito", which is just not true at all.
First of all, let's get the obvious out of the way; anyone with RCT output can kill Mahito regardless of whether they have soul damage or not. Regardless of how Idle Transfiguration works, Mahito will always be a curse and have the same weaknesses of any curse. Also, it should be pretty obvious that any lethal domain has the capability of killing Mahito. We know that domains can easily bypass the effects of cursed techniques (as seen with Gojo's infinity), so Mahito cannot protect himself from opposing domains unless he risks using his own domain.
Now, to get to the main point; a sorcerer without soul damage can kill Mahito. Many think otherwise, but it's the truth. Because, like any other technique, Idle Transfiguration requires cursed energy to be activated and be used. Mahito does have an absurd amount of cursed energy, but he doesn't have infinite cursed energy and thus he can't use Idle Transfiguration forever.
Additionally, Idle Transfiguration has been shown to make Mahito feel some degree of "burn out" if used at a larger scale. During the Shibuya Incident, Mahito was shown to be "nerfed" to a degree when he created a clone of himself. His clone couldn't even output Idle Transfiguration, and the original Mahito was stated to be weaker overall after creating his clone. So there is evidence pointing towards the fact that it does take a considerable amount of cursed energy to heal/recreate large parts of his body. So if you are able to frequently destroy large chunks of Mahito's body, he will eventually run out of cursed energy.
Furthermore, Mahito cannot create flesh out of "thin air". Every time we see Mahito use Idle Transfiguration, any flesh created always stems from pre-existing flesh. For example, if Mahito's arm were to be cut off, to make a new arm he would have to create new flesh from his shoulder or another pre-existing point/area of his body. This means that if you were to destroy the entirety of Mahito's body (regardless if you have soul damage or not), he would have no flesh to create new flesh from, and thus would be unable to heal himself.
TlDr; Mahito requires cursed energy to use his technique, and his technique itself requires Mahito to a) use more cursed energy to recreate large portions of his body and b) have some pre-existing flesh to make new flesh from. Thus, you do not need soul damage to kill Mahito. Sure, it is the safest and most efficient way to kill him, but there are other ways too. If you are able to destroy large portions of his body, destroy is entire body, force him to waste excessive amounts of cursed energy, etc, then you have a pretty surefire way of winning against him.