It could also be a side-effect of Makima´s domination/subjugation
In a sense, since she is a devil, one of the fears people have thanks to chirstianity is that when they die they will be dominated by the devil.
So maybe her powers allows for a person soul/counsioness or whatever to linger even after their body is killed, and, maybe, even allow for ressurection.
For how sad/scary it is to not even be able to decide/have your own death withouth Makima/Domination saying you can die?
On that sense, considering that
A) Makima is being setup as the big bad or at the very least the final fight (as she seems stronger than the Gun Devil, not in a destructive sense ofc)
B) We saw some chain-like things binding her "puppets" before the fight
C) Chainsaws being pretty much the most powerfull "cutting" object we humans have in our subconcious,*
I´d say Pochita/Denji true identity is the Devil of Rebellion.
Arguably, a ever present fear in our lifes (subordinates, children, students, opressed people), but, at the same time, a symbol of hope, an antithesis in and of itself.
Which would explain why the Chainsaw Devil hunts other devils,
Why Denji has to sacrifice a lot of blood in order to get his powers going, as a true rebellion is never a free, easy thing, it has to be earned.
Why Makima is interessed in subbding him, either she actually has the hots for her total oposite, or by finally bending it to her will, achieving unprecedent levels of power.
Why blood (the very fuel of a violent rebellion) keeps it going indefinitally, since as long as the people want a rebellion can keep going (Even if it does end up losing it´s sense, just like Denji loses himself in combat)
And why many devils seem to fear it, even if by it´s power level it shouldn´t be able to stand up to some of the foes we have seen until now.
Since a Rebellion, by its very definition, its about the overtrowing of a stronger power by a (percivied as) weaker power. Hence, kinda of a conceptual ability of always having the chance to turn battles around.
Oh and as to why Pochita is so afraid of Denji going past that door? Well, rebelions are never a beautifull thing, aren´t they? Just go and study any in our real life story.
*Building on B and C points, CUT AWAY THOSE CHAINS OF DOMINATION, DENJI!