Leverage is basically the same as margin, which is using stock shares or cryptocurrency (I'll just use "shares" for the remainder of this comment) that you own as collateral for a loan to buy more shares. It's often given as a ratio, like 2X. This means that if you buy $100 worth of shares, you can borrow another $100 worth and own $200 worth.

The catch is that if the value of the asset drops, you still need to be able to cover your loan with the asset. So if you bought 1 share for $100, you can leverage it to buy 1 additional share. But it's important to note that the actual cash value of your account is still only $100.

If the share price drops to $50, then you will likely face liquidation. Why? Because you're still responsible for the $100 loan. If you get liquidated, you're forced to sell your two shares for $50 each, $100 total. But then you have to pay back the loan, so you end up with $0.

The upside, however, is that if the share price went up to $150, you could sell your two shares for $150 each ($300 total), pay back the $100 loan, and end up with $200 net.

> and if there are (or not) any mild-leverage alternatives without liquidation

The only way to do this is to borrow at a lower ratio. ie, $100 of your own cash, then borrow $20 to buy 0.2 shares. The $100 share price would have to drop to ~$17 before liquidation occurs.

For brokers to remain solvent, liquidation must occur if the value of the asset drops below the value of the loan.