Character Controller and Reverse Gravity

Question

So I have a Game object with Rigid Body, a Character controller and my Movement script. On a specific condition I am reversing gravity. The problem is that the velocity.Y when the gravity is reversed, keeps increasing to the infinity. If I try to reset it like in the first if statement (which works for normal gravity) the object keeps bouncing from the ground. Gravity scale is either 1 or -1 in order to reverse gravity and movement.

This is the code:

 void Update()
    {
        
        _isGrounded = Physics.CheckSphere(groundCheck.position, 0.4f, whatIsGround);
        Move();
    }

void Move(){
//Reseting States for new cycle , unless the object is falling
        if ((_isGrounded && velocity.y < 0))
        {
            velocity.y = -2f;
            _isRunning = false;
            _isJumping = false;
            _isFalling = false;
        }else if (velocity.y < 0 && !_isGrounded)
        {
            _isFalling = true;
        }
        //Moving on X axis
        float x = Input.GetAxis(KeyInputMove);
        if (x != 0)
        {
            _isRunning = true;
        }
        moveDirection = gravityScale*_transform.right * x;
        _controller.Move(moveDirection * moveSpeed * Time.deltaTime);

        //Perfoming jump
        if (Input.GetButtonDown(KeyInputJump) && _isGrounded)
        {
            velocity.y = (float) Math.Sqrt(1 * -2f * globalGravity);
            _isJumping = true;
        }
        
        velocity.y += gravityScale * globalGravity * Time.deltaTime;
        _controller.Move(velocity * Time.deltaTime);
//Updating animation states 
        _animator.SetBool("Grounded",_isGrounded);//^This is the idle state
        _animator.SetBool("Running",_isRunning);
        _animator.SetBool("Jumping",_isJumping);
        _animator.SetBool("Falling",_isFalling);

    }
    
   
    
    private void OnTriggerExit(Collider other)
    {
       //Reverse Gravity and Model Rotation
        if (other.gameObject.tag == "Portal")
        {
            _transform.Rotate(0,0,gravityScale*180);
            gravityScale *= -1;
        }
    }

Answer 1

The problem is that the velocity.Y when the gravity is reversed , keeps increasing to the infinity.

That's what your code tells it to do:

velocity.y += gravityScale * globalGravity * Time.deltaTime;

Perhaps you are forgetting to check if the gravity is negative or positive when determining whether the object is falling. Here's what you probably want:

if (gravityScale > 0 && velocity.y < 0) 
    || (gravityScale < 0 && velocity.y > 0)) 
{
    _isFalling = true;
} else {
    _isFalling = false;
}

if (_isGrounded && _isFalling) {
    velocity.y = -2f * gravityScale; //maybe you should just set it to 0?
    _isRunning = false;
    _isJumping = false;
    _isFalling = false;
}

I assume that gravityScale is 1 when gravity is normal (objects fall downward) and -1 when gravity is reversed (objects fall upward?). I'm not really sure why you are setting the velocity to -2 in the first if condition; you might want to try setting it to 0.