Money
Money demonstrates what numismatists term conceptual immortality. Individual banknotes deteriorate, coins erode, yet the abstraction of monetary value persists across millennia. Currency predates Superman by approximately four thousand years and shows no signs of obsolescence.
Even physical destruction of monetary instruments proves ineffective. Burn a banknote, and central banks issue replacements. Collapse a currency, and alternatives emerge within months. Money, like entropy, cannot be eliminated, only redistributed.
Superman
Superman's durability, whilst exceptional by biological standards, demonstrates alarming inconsistency. Main DC continuity records four canonical deaths, with additional demises across alternate universes and elseworlds. Each resurrection requires increasingly elaborate narrative justification.
Moreover, Superman remains vulnerable to Kryptonite, magic, and editorial mandates. Money recognises no equivalent weaknesses. There exists no financial Kryptonite capable of nullifying currency's fundamental properties.