Well a iPhone 6 really bend if you keep it in a OtterBox, and use it with the belt clip?

If you install it correctly in the Otter Box it should not bend if it is the correct case. It will not bend taking it in and out of the case. If you sit on it while it is in your back pocket it might bend.

Anything will bend if you put enough pressure on it.

No, you have to apply a good amount of pressure to bend it. Just having it in your hand will not do so.