Not a bad loss, it's gambling after all. You win some, you lose some that's just how gambling works. If he happens to win his bet would that be terrible?
IMO, most gamblers has poor gambling records though. I bet most of us has lost more money than we win.
I could only say that it's a terrible loss if someone has to take a loan just to place a bet and lost it eventually, that is a prime example of a terrible loss. But as for Drake, $850k isn't a big deal as he owns a lot of money. If I'm as wealthy as Drake I could've done the same thing, bet on the most risky but high reward odds since money doesn't bother me at all so why not maximize the profitability chances.
There are not a lot of successful gamblers who consistent make profit and everybody who gambles will have losses and wins. Drake, with his crazy high bets, just gets a lot of attention from everybody and everyone has his opinion. To be honest, a lot of his recent high bets were all a loss though, so I wouldn't follow Drake his bets lol.