What if Kris in Deltarune was Frisk all along?
(A what-if scenario)
summary: Frisk renamed themselves as Kris, but in the process, forgot the player, and who they were. That’s why Kris treats the soul as an enemy.
At some point in time, after the events of Undertale's True Pacifist ending, Frisk wanted to be a new person entirely. They wanted to choose who they were in this world.
So, they changed their name to Kris, and also adopted a look similar to Chara. They did this while they were still a kid, which is why Kris' childhood is explained in the game.
We eventually stopped playing Undertale, and during the time it took between Undertale and Deltarune Chapter 1, Kris enjoyed their new life. However, they also experienced personality changes that made them who they were now. They slowly became an introvert, but also found an interest in piano, and mischievous pranking.
Eventually, by the time Deltarune Chapter 1 released, Kris grew up to be a teenager. By this point in time, they had forgotten about the Player entirely (or the Soul) despite their many adventures in Undertale. They seemingly enjoyed their life without it.
But when we returned, we ended up in Frisk (or Kris)'s body again. Not remembering this is how they used to be, Frisk (as Kris now) has inherent hatred over the Player. They now realized how the Player's existence restricted their choices. They also remember everything you made them do from long ago in the Undertale events, only the bad ones (like genocide).
What resulted from this is a long eternal rivalry between the Player and Frisk (now known as Kris), to the point Kris is also willing to relentlessly beat down the Player's form (the SOUL), forgetting that we are their friend.
If only the player somehow managed to remind Frisk (or Kris) about what good things we did for them back in the Underground,
they both may come to an understanding.
But for now, it's gonna be hockey stick whacking soul 9000 times
