If an investor buys top altcoin or BTC, he cannot lose everything, because these projects will not go bankrupt too soon. Their price will fluctuate, but will not lose until it sells at a lower price than the investment price.
He can lose the value of bitcoin or altcoin because the price of bitcoin and altcoin will always fluctuate, and we don't know when the price will increase or decrease. There is no guarantee that the project can continue the work even if the project is one of the top altcoins at the market. So you need to be careful to select the coins. But yes, with investing in the bitcoin or the top altcoin, that can give the investor a profit in the short term and long term.