Winning 1/500,000 twice is MUCH less likely than winning 1/1,000,000 once.

If two events are independent, meaning that the outcome of one does not impact the probability of another, then you can find the probability of both events occurring by multiplying their probabilities.

The probability of winning with a 1/500,000 probability twice is 1/500,000^2, or 1/250,000,000,000, which is 250,000 times less likely than winning with a 1/1,000,000 probability