XANA was the main antagonist of the French animated television series Code Lyoko which aired on Cartoon Network years ago. XANA was originally a multi-agent program created by Aelita's father Franz Hooper to destroy Project Carthage. However, as with most artificial intelligences, XANA quickly goes against its programming and tried to destroy humanity only to be trapped in Lyoko alongside Aelita and her father.
Eventually, the supercomputer is eventually reactivated and XANA becomes a constant foe against the Lyoko Warriors. Throughout the series, XANA would try to destroy humanity in needlessly horrific ways such as trying to electrocute the entire student body in a cafeteria with electric wires, trying to cause a nuclear meltdown, attempting to crash a train carrying toxic chemicals, creating music to render people into comas...the list goes on. After the first few seasons, XANA would gradually alter its plans where one of its goals was to take over the world by escaping into the internet to create a robot army as well as make Aelita its eternal slave.
Now while robots, supercomputers, or programs would often tend to lack agency because they would be programmed to do these acts (think of AUTO from WALL-E who was programmed to keep the people from returning to Earth as it was inhabitable). With XANA, however, it was created simply to counteract Project Carthage. But much like with Skynet of the Terminator franchise, XANA became self-aware and all of its acts later on are solely of its own volition. It chose to rebel against its creator rather than the other way around. As for whether or not it has a personality...yes, it does. It continuously tries to exterminate humanity in needlessly sadistic fashion which firmly removes it from being a generic doomsday villain. In one of its appearances where it manifests before the Lyoko Warriors? It reveals itself as being an overly sadistic beast who takes delight in trying to kill them. There are a few moments where XANA is forced to work with the Lyoko Warriors when they have a common enemy such as appearing to be appreciative by having its monsters bow before the Warriors, but in XANA's next team ups, he returns to trying to kill the Lyoko Warriors even when they have a common enemy.
Nothing to be said on the heinous standard as XANA frequently tries to kill off humanity in terrible ways and has a lot of resources.