Why disconnecting one outlet kills power in other outlets?
The evidence gleaned from your question and the conversation in comments strongly suggests that the shorting bar between the top and bottom half of a &quot;partial switched outlet&quot; has not been removed. If it has been already removed from the outlet that you have open then there is a strong possibility that there is another switched outlet on that circuit.
The cable in the switch box with the red wire may very well daisy chain to another outlet box before eventually terminating at the outlet box that you have open. Check all other outlets on that circuit to see if you find a box with the red wire cable both entering and leaving the box. Good chance that the shorting bar at that location has not been removed.