legal, the king of alcoins is ethereum in this forum no one disagrees if ethereum is the king of alcoins, this proves ethereum is a big coin and in the future ethereum coin cannot be competed with other alcoins, if btc is destroyed can ethereum replace btc ?
The topic can be quite subjective, IMO. Other people can have a different view on this because they are trailing a different coin as there a other altcoins that boast a much bigger growth in the past year but just like what I've said, it's subjective. But in terms of trading volume per day, ETH can be hailed as the king of altcoins and it has been listed on the Forbes as #1 among altcoin's category.
if btc is destroyed can ethereum replace btc ?
Quite impossible, I reckon. But if bitcoin will vanish or from your words, is destroyed, top altcoins like ETH are also expected to follow the trend.