Usually it comes down to whoever can utilize an especially potent action at the right time such as the Dragon Fire action that banishes one character on the spot to give them the momentum they need to win the game
Any abilities that trigger when a creature with a certain power enters the battlefield, such as that of Mentor of the Meek, will see the token enter as a 0/0 creature before it gets +1/+1 counters
Many a green mage was seen conceding after they had no answers to a turn six King Crab with four green creatures already on the board
For Murders of Karlov Manor (MKM), Outlaws of Thunder Junction (OTJ), Modern Horizons 3, and Duskmourn: House of Horror (MH3) sets, you can redeem up to 5 Prerelease codes per MTG Arena account
That difficulty only becomes a greater burden as you add more colors, but by using lands with basic land types, you can mitigate this problem by making use of helpers like Polluted Delta, Skyshroud Claim, and Knight of the White Orchid to find them and put them onto the battlefield quickly