I know almost nothing about knife fighting and I am sure there are a lot of good choices. But I've handled one of the first gen Temperance a few times and it is the most weaponized knife I've ever held.
This is the Temperance 2:



Maybe it depends on what knife fighting style?
For a cheap stabbing type knife, the Glock knife isn't too bad. You can even sharpen the swedge...



For chopping zombies in half you could get something like the Becker Combat Bowie.


Cold steel has a lot of affordable knives theoretically designed for fighting, if you can get past their ridonkulous marketing.