Decentralised “Risk-Free” Interest Rate. Towards Crypto Fractional Reserve

I don't understand how it can be risk free.

If I promise an interest rate of 100% in a week, and I convince a lot of people to deposit coins in my node, who will force me to pay the interest?

I'm not sure if this applies to all PoS, but IIRC in the Ethereum proposal, if the node misbehave the coins in the stack are frozen/lost forever. What happens in this case? Are the coins deposited in the node also frozen/lost? Can I make a fake account and deposit the coins from my fake account into my official node, so my node can misbehave and my coins are safe?