Nothing is too big to fail in crypto world, Terra Luna is a big example that the safety of your money isn't guaranteed even if you invest in top altcoins out there, it's the same risk involve with crypto generally including BTC but BTC is just way safer, I have seen people losing 6 figures to Luna and some Defi projects, first of all try to understand what you are going into, many don't know how risky crypto space is, take risks with what you are ready to throw away.
But if we talk about Bitcoin, the prime mover, then we have some exceptions to this rule. Terra Luna fall because of the people behind it, they didn't know or at least didn't expect this and don't have any fall back until it's too late. Of course there is risk, so everyone should know how to mitigate them at least and not invest all your money into crypto and hope that one day you will become a millionaire. Maybe ETH is also one project that you can add to the list of being a 'safe' investment.