It's pretty well impossible to have one without the either as it does take energy to get the projective there to create the hole. I think it's important to understand how bullets kill so we can make better decisions when placing shots and selecting bullets. Highly frangible bullets are a poor choice for large game yet they "dump" all their energy in an animal where a well constructed bullet uses that same amount of energy to achieve penetration. How the bullet works with the energy is far more important than what that energy does to the animal. Because in the case of highly frangible bullets, we see that energy is basically useless when talking large game. With a well constructed bullet, it's very useful.

I think it's also important to realize how important shot placement is and despite the odd lucky shot, unless you hit a vital organ or major blood supply the animal may not be killed. Talk of shots in the leg stopping the heart aren't something I'd like to see promoted because the majority of the time they don't. Yes, energy is required for a bullet to do its job but that about the only thing energy is responsible for in 90+% of cases from the research I've done.