If you hadn't noticed, Kris walks noticeably slower in this video than they do in base Deltarune.

That's because while you're on this path, they'll try to hinder you as much as they can with the little control over their body they have in their possessed state.

The ways they'll do this include slowing down movement, and in battle they'll intentionally miss attacks. Even though that comes with the risk of death, they know they'll survive due to knowledge of the player's control over their world.

In Kris' perspective, hindering the player allows more potential victims of the player's slaughter to live as long as possible. Ultimately, on this path, the Darkners from the Dark World they visit will die along with their fountain, rather than become part of Castle Town, but Kris would rather spare them from their own wrath, as to avoid the player gaining enough power to harm more people.