Well that would be stablecoin. If you want an altcoin thats not perceived btc's price then thats totally impossible. Most alts are also paired with btc and even so, btc crash would likely affect other tokens too and worse much bigger down. Thats the thing about altcoins you could gain 10x to 100x but also the down can be 90% like what happened last year after the bull run season. Most coins are down.