[@Dezuel]

Apparently, it would take lots of focus to pull off the instant-kill punch. In the game Ben belonged to, most of the characters would have special attacks that would provide a surefire way of hitting the opponent. Ben's special, on the other hand, is very powerful but can be blocked or dodged. He needs to know where he'll start shifting the impact of the punch, so if he was aiming for the target's stomach but hits his/her arm instead, his body won't be able to move as quickly as his mind and the attack would be a failure. Because of that, he only uses it to end combos.

[quote=@Dezuel]
Would the impact shift be possible to use on objects or like for example walls or the ground in order to produce a large crack that will split it in two or punch the air to create a shockwave that may extinquish a fireball?
Just since we've kind of want to avoid one-hit-KO's. 
[/quote]

Yeah. Something like that.