Throughout Squid Game, Gi-hun faces a series of deadly challenges, but his final bet in the Netflix show was the most significant risk of all. In Squid Game, a series where desperate people compete against each other in six deadly challenges for prize money, Seong Gi-hun (Lee Jung-jae) somehow befriends the Old Man/Oh Il-nam (Oh Yeong-su). It's a heartbreaking friendship, with Il-nam even apparently making the ultimate sacrifice and giving up his life for Gi-hun by letting his friend win at the marble game in episode 6. The decision seemed to seal Il-nam's fate. However, the finale revealed a twist. It turns out Il-nam didn't die after all. In fact, he was even one of the architects of the game.
The twist reframes Il-nam and Gi-hun's entire relationship. While Gi-hun and hundreds of other players risked their lives during Squid Game, Il-nam's life was never in danger. The marble game proves it. While all the other losers in the marble game met their demise, Il-nam simply exits the tournament after losing. Similarly, other games Il-nam competed in, such as Squid Game's tug-of-war, were likely rigged in his favor as well.
Despite the dangers of Squid Game, Gi-hun's final competition almost cost him more than his life. Gi-hun discovers Il-nam is alive in the finale, and the latter challenges him to one last game. Gi-hun meets Il-nam on the 7th floor of a building, which signifies the 7th game in Squid Game, and the Old Man proposes a wager. Il-nam bets Gi-hun that no one will help a man who's freezing outside on the street before midnight. Gi-hun is willing to play but says if he wins, he's going to kill the Old Man. As a wager, Gi-hun adds that he'll bet, "Anything." However, his bet may be a bit more specific than the show lets on. Gi-hun is playing for his soul.
The Old Man orchestrated the game to break Gi-hun's faith in humanity. Gi-hun still believes in the goodness of people, and Il-nam wants that to end. "Do you really still trust people," Il-nam asks when the game looks to be going in his favor. If Gi-hun would've lost, he'd lose all faith in humanity and himself as well. However, someone eventually helps the freezing man, and Gi-hun wins. As another nod to the fact that Gi-hun was betting his soul, the Old Man dies as Gi-hun wins the competition.
Though Gi-hun retains his soul, his faith in humanity is still in jeopardy. He could've quickly gone and helped the freezing man on the street, instantly winning the game. But Gi-hun didn't go. Instead, he simply remained with the Old Man, watching to see if someone else would help. So the idea that Gi-hun becomes corrupted and eventually joins the games in Squid Game season 2 remains a possibility. After all, the series director, Hwang Dong-Hyuk, already teased that Gi-hun could go over to the dark side.