If you are trying to cut heavy electrical wire with side cutters that have seen better days, here is a hack that will make it easy.
I ran into a situation where I was doing some electrical work for a relative. I needed to cut some #12 wire. I had a set of side cutters available that had seen better days. I have a strong grip but trying to cut the wire was difficult.
Fortunately there was a sturdy, small vise on the workbench. I simply put the wire in the side cutters and positioned the handles in the vise jaws. A quick turn of the vise handle and the wire was cleanly cut.