Does copper exacerbate wounds?
Excess copper in the body can be toxic but I'm not sure a copper blade would be especially toxic unless it was coated with something else or it remained in the wound. Copper can be acutely toxic when ingested, or chronically over a long period of exposure (like lead), but is more often associated with a failure in copper excretion. Since the body has ways of dealing with excess copper, I just don't see much merit in the super-toxic copper blade, unless it is designed to break off in the target.