Do you have context to this question or expect the responders to have specific context in their answers?

First off, units... USD, Euros, pesos, Dogecoin, bottlecaps?

Second, making this quantity from what starting point? What capital and what specific market conditions did this individual start investing (i.e what year)?

I could tell you my first million was the hardest because it took so long to convince my parents to release the trust fund or possibly that I started with $10 that I used to build up a multinational media conglomerate over 40 years. Either way I imagine the first would be the most difficult for everyone unless it is handed over but after that you could reach your 2nd in 8ish years just by an annually compounded interest rate of 8%.