Attach a body gyro to the characters humanoid root part. Since you only want the player to rotate on the y-axis, set the max torque to 0 and x and z.
Then, through the run service, every frame set the cframe of the body gyro to the mouse’s position.
Note that body gyro’s are deprecated and have been for a while so you might want to use the more modern version but I can’t remember the name.
Also, you could not even use forces at all, instead, in the run service thing I talked about earlier you could set the character’s cframe to look at the mouse using cframe.lookAt or something equivalent.