Makima is the main antagonist of Chainsaw Man and is also the Control Devil. At the start of the series, she could be mistaken as a sort of mentor figure for Denji similar to Gojo to Itadori in Jujutsu Kaisen. She saves his life, provides him with a purpose for living, and also helps him in making use of his powers.
This even leads to Denji finding friends and other connections, something that would’ve been impossible if he had never met Makima. She does have a lot of shady dealings and doesn’t seem to care much about human life in general but that isn’t enough to label her as evil or a villain.
However, later on, in the series, we find out that Makima had done all this just so that she could emotionally manipulate Denji. It turned out that she had given Denji the means to form relationships with Reze, Aki, Power, and several others just so she could snatch them away later. This would break his heart while giving him no one to lean on but Makima herself.
As we know from several other Shounen series’, no matter how terrible the action of a person if they have a sad backstory then that leads us to empathize with and possibly even end up liking them. This is the complete opposite in Makima’s case. Her end goal seems to be to build a world without any sort of tragedy or grievance and she plans on doing that by controlling the Chainsaw Devil.
She is willing to do anything it takes to achieve this without a care about who it affects or who she has to use. She might have even possibly ended up killing more people than what the Devils she planned on erasing themselves would have.
There seems to be no reason as to what forged her goal and the only thing we know about her is that she is a fanatic towards the being known as Chainsaw Man. So in conclusion, we can say that Makima is one of the Evilest Beings to ever grace animanga and is up there with the likes of Griffith and Aizen.