Bending the rope at a small angle is what causes the weakness, in my understanding. So, you want to avoid tight bends where you attach the rope.
I made a couple of devices out of some small steel cable and some 3 inch pipe nipples and 3 ferrules per device. See the attached picture.
I used good quality paracord. That was a bad choice because paracord keeps a lot of strength when it's tied in knots. The cord often failed between the knots. Next time, I'll use something different
Our plan was to have each patrol tie a knot on one side and see whose knot was the strongest.
If you have some weak enough rope and a couple of 5 gallon buckets, you could suspend the buckets from the rope and add sand until the rope fails.