It's here, it's here! Thanks to DarkErazor it's here!
Jak has a kill confirm that is not wall-reliant, and can be done from a grounded position!
EDIT: In some further tests, I have found that it DOES work from the air. You just have to be very close to the ground before releasing the charged blast. (Otherwise it sends them flying too far)
It's also important to note that you can turn while holding the charge in the air, which is great if you need to reorient yourself because your enemy did.
EDIT 2: This doesn't appear to work as well with some characters. These same characters can usually be combo-ed into with a simple backwards concussive blast, so there's a workaround. (Credit: Xarf)
EDIT 3: Added a video for this. ^^^
The simple-yet-selective confirm:
I've read it in the kill confirm thread. This could potentially help out Jak players a lot.
I see it as too hard to pull off myself. The other player has to let you charge up or walk up to while you are about to obtain a charge. But jax does now have a "practical" kill confirm.