or you can target the opponents head and pull it from body with strong force

I think its all to do with physics.

If your hand is grabbing the middle/lower back of your opponents head and using wrist, elbow, shoulder, pecs and chest to pull it towards you, it will create a lot of pressure on the neck. The combined force of all of these joints moving in the same direction WHILE your opponent is moving in the opposite direction would be enough to cause the required amount of tension on the neck joint to dismember it.

The bottom of the head would work better for a few reasons:

1. The hand would touch the neck, causing a small amount of damage and lowering the amount of tension required to make a dismember.
2. The hand would go in the gap between the neck and the head, cause much much more tension (I have noticed that putting something between that gap makes for a very easy dismember)

Hope this has helped with your question

Well yeah but you don't grab the head to rip off head, you grab the neck... Though it is very rare to just pull of the head not grabbing his neck, you would need ALOOOOOOT of force though

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