In my Jump and Run game you don't get damage when you're are colliding into the enemy from the back but it's working when you're hitting it from it's front. I'm using a Kinematicbody2d for both the enemy and the player and an area2d for checking collision with the player. The enemy is slower than the player so if you are hitting it from the back you are slower too but you can see in the image that the colliders are not touching.
click to see the picture
I tried messing around with the setting or making the colliders bigger but nothing worked