Let's use same example of stock at $100. If you buy its 2x ETF, let's say the 2x ETF is at $40
When stock drop 30% ($100 to $70), your 2x will drop 60%, so $40 becomes $16.
Now, stock rallies 40% to come back ($70 to $100), your 2x will rally 80%, but it can only come to $29. ($16 to $29)
In this example, even though the stock does not move, your 2x lost 33% of the value.
Deep ITM leap does not suffer from this kind of decay
