I really want to know which alt you mean because I believe most altcoins will follow the bitcoin price trend so far. IMO, the current average of the top altcoins have fallen by more than 80% since their last ATH, I can expand the list here for comparison.

The following is the current market condition regarding the percentage decline in bitcoin prices and top altcoins after last year's bitcoin ATH.

Bitcoin - [-71.3%]
Ethereum - [-78%]
BNB - [-69.5%]
Cardano - [-84.9%]
XRP - [-90.6%]
SOLANA - [-87.1%]
Polkadot - [-86.6%]
TRON - [-73.7%]
LEO - [-36.5%]
Shiba Inu - [-90.6%]