What is the safest ETF to buy?

Could you please enlighten me on what constitutes the safest ETF to invest in? Given the volatile nature of the markets, I'm seeking a secure yet potentially profitable option. Could you recommend any specific ETFs that have demonstrated stability and consistent returns over time? Additionally, what factors should I consider when evaluating the safety of an ETF? Is it primarily based on its track record, asset allocation, or perhaps something else? Thank you for your insights.