Inverse ETFs are So Different from "Traditional ETFs"

ETFs were originally seen as less risky as you invest in a basket of index stocks e.g. $SPDR S&P 500 ETF(SPY.US)$ but they have come out with more and more products and the risk level has gone up with Leveraged ETFs like $ProShares UltraPro QQQ ETF(TQQQ.US)$ and even Inverse ETFs like $ProShares UltraPro Short QQQ ETF(SQQQ.US)$. Quite interesting to have a look at their respective portfolios via Detailed Quotes > Components as screenshot below: