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%]
This!! For real tho, makes you wonder which alt that op has. And it's really obvious that most altcoins at the time were in the bottom. At least today's prices seems a bit a lot better than before. It's scary to think that even major altcoins could have fallen that deep.
So far, bitcoin still holds the wheels, when it dumps then alts will also suffer from it. Tho some other factors played a part in it as well, such as volatility, news and all.