Flowey is a science experiment gone wrong. He is a soulless flower with the liquid embodiment of the human trait of determination injected into it with the dust of the deceased monster Asriel. This created an emotionless flower with no sense of mercy or love, the determination gave him the power to manipulate time. So he starts exploring every possible choice he could make with his power. In UNDERTALE and OUTERTALE, he tries to kill you immediately after meeting him. He spies on you throughout the game and intervenes during ending in a quest for power. In OUTERTALE specifically, he learned how to hack and mess with technology at terrifying levels. He at one point hijacks the queen's spaceship causing it to crashland on an icy planet in chapter 1. In UNDERFELL, when he meets you, unlike UNDERTALE and OUTERTALE, he does not pretend to be friendly as an attempt to steal your soul. Rather, he tries to help you escape knowing how dangerous it is out there. (And perhaps he might turn on you for that soul of yours...)