With Proof: Index fund v/s actively managed Mutual fund for 20+ years

I guess this is the most asked & debatable question but yet its not clear while we got the audience of both the side but noonr have provided the reasons with the fact and historical data that which one is actually best in a long run for say 20-25year.
Is there a proof that Investing in any 1 Index fund, for say Nifty 50 will give better return than holding 3-4 Mutual fund or other way round?

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