I explored a few different ways to kill a chicken. I wanted death to be swift and as painless as possible and to be the least traumatic for me as possible. I found what I feel is the best advice from a poultry vet and if it's allowed, I'm posting a link to the article because a picture is worth a thousand words.
http://www.the-chicken-chick.com/2017/02/how-to-humanely-euthanize-chicken-by-dr.html
I have been doing the cervical dislocation described in the article I linked before I cut the head off (I hold the legs to scald them), but I have been pondering the notion of decapitating the bird with large loppers similar to what you posted. According to the vet, a clean decapitation takes about 15-20 seconds to kill the bird versus about 40 seconds using cervical dislocation. Forty seconds is, IMO, way too long, but if the bird is unconscious, does the difference between 15 and 40 seconds matter? I'm exploring the lopper method because it seems more controllable than winding up a grand swing with a machete and possibly missing the mark in that last fraction of a second.