Any knife with bad edge geometry, and unergonimic handle and design that does not keep or hold an edge would be a "Bad" knife. Also anything ridiculous and cheesy and overpriced unless it is so far overboard that it actually becomes cool for it's camp value.
I used to be really into BusseKin knives and I found a definite range of how well they worked as bush tools but the better ones worked very very well and the ones that did not were usually meant for some other kind of purpose like fighting or just collector knives. My flat ground 8 inch SH-E is a very handy bush knife.
Now it takes more than just working really well to make me happy. I want it to look good and preferably timeless. I like natural materials like wood and leather with carbon steels ,often blued. I think that we should be able to have a beautiful warm wood handles and leather scabbards with all the performance of the best modern knives. I also like the old classic shapes for blades. I find that if a blade shape has been popular for a 1000 years it probably works very well.
I especially like the shape of these knives.
My favourite is the second from the bottom ,the Rosarms Bayonet is a classic shape you don't see much anymore with no drop to the point.
The Skookum also has a no drop point.
I also like hollow grinds even if they are not seen much any more.