I want to have the force or last velocity that the player hit the ground, so if the fall is higher, the impact is bigger.
My objective is apply a camera shake (already set up) based on the impact force, and maybe some animations
A kinematic body's velocity is set by you, so when you detect a collision with the TileMap, check what your body's velocity variable is.
I tried with area2d, for example, when body enters: print (motion.y)
sometimes it prints 0, sometimes a velocity, so i think this is not the better way to do it, or i'm doing it wrong
Well, an Area2D should have nothing to do with it at all. When your kinematic body collides, it will report the collision.
I suggest reading this: https://docs.godotengine.org/en/3.2/tutorials/physics/using_kinematic_body_2d.html