Which knot?

[Predestinated]

Some people say the sklipknot is the best knot for hanging. Others say the hangmans knot is. But I need something better:

I need a knot, that makes the loop automatically smaller, when someone puts pressure/weight on the loop. (My mom used to make these type of knots with plastic bags: you put pressure on loop and it gets smaller, without having to pull the knot.)

Whats the name of that kind of knot?

Thanks!

 

[Deformationalplagio]

Slipknot does this :p

 

[Predestinated]

Another important question: As you can see on the picture, one side of the loop is crooked / skewed. (Look at the red lines) I've tried with different types of slipknots, but one side is always skewed.

Is this bad for hanging? Because imagine my finger was my neck. Then one side of the neck will have more pressure than the other side. Could this cause problems?