It annoys me to no end to see Flowey/Asriel watered down to "evil monster who wants to see everyone dead" or "sweet baby who didn't really want to hurt anyone " and NO in-between.
He's actually one of the most complex characters in the whole game in my opinion.
People forget that he's a kid who is somewhat manipulated into dying by his best friend and then ends up with godlike powers.
His first instinct after coming back to life is to call for his parents. His next is to try and help people. It isn't until he realizes that he can't really do anything significant with his ability that he starts to kill out of frustration and curiosity, while having the knowledge that if he does anything "too bad" he can just fix it. And when he realizes that he CAN'T reset and fix whatever goes wrong, he stops. He doesn't try and hurt ANYONE throughout the game up until Asgore, when he knows he's in a position to regain the ability to reset. And even then, his only real goal is to keep you around.
He claims to not be able to feel positive emotions or empathy, but there's actually evidence to the contrary within the game and outside dialogue. He has been shown to genuinely like Papyrus, and he feels sorry for Toriel when she she falls asleep drunk in Sans and Papyrus's garage. He can clearly feel fear, as shown at the end of the genocide route. He also has personally admitted to being suicidal on the genocide run.
Death is one of the worst traumas to experience, and numbness is an extremely common traumatic response. It's no surprise that he "feels nothing" when he comes back. 8 year olds aren't exactly well known for their morality and sound judgment. It's really not surprising that he jumps to the conclusion that he's numb because he doesn't have a soul anymore. And understandable why he takes the actions he does.
Being stuck trying to do good with no clear result and repeating the same things over and over for what is insinuated to be the equivalent of a few hundred years would drive even the most stable person insane.
It isn't until his God of Hyperdeath fight that you get to actually see his true side: A dramatic and scared little kid who misses having a friend who understands him, and who has fallen into the role of a "villian" and doesn't see the point in being better. After you show him that he CAN be better, he calms down and reevaluates his perspective a bit. Even going so far to tell you to make him forget if you reset afterwards.
A lot of people give credit to him having a soul at that point, but I feel it has much more with him starting to heal from the trauma that he was forced to go though and the additional trauma he put himself through. Also, the trope of being a villian just because they have no empathy is quite ableist, and it feels unlike Toby to play into that.
