I thought you were going to show knives with busted tips or chunks missing from the edge of the blade. Whoever did that to the knives should learn how to use a knife!
If they insist you fix them, there are a couple of ways to do it. If you choose to use a grinder, a slow speed grinder is best. You probably don’t have one and good ones are not cheap. The same with belt sanders.
Of the two tools mentioned, I would suggest the belt sander, either a 1x42 or a 2x42 slow speed. Get a bucket of water. As you grind, go slow and keep your fingers near where you are grinding. As soon as you feel heat, the blade and your fingers go in the bucket. It will take a while to grind a proper tang.
I would charge more than all three knives are worth to fix one.
When my customers bring me things like that, I tell them to save the repair money and spend it on a new knife.
Kevin