Despite forming on the stronger of the two starting tribes, the Onion Alliance was decimated by a series of twists and strategic misjudgements. Susie Smith's unexpected flip from the alliance sealed its downfall, but the alliance still managed to produce the winner of the season. It was called the Onion Alliance because Marcus Lehman said it was an alliance with multiple layers, him and Charlie Herschel being the innermost layer.
The First Layer
The alliance was formed by Marcus Lehman, when he and Charlie Herschel bonded at the Kota camp. Later, they recruited Corinne Kaplan and Jacquie Berg. Marcus' original idea was to construct an alliance like an onion with many layers; he and Charlie being the core, Corinne and Jacquie being the outer layer, and so forth.
On Day 9, Corinne recruited Bob Crowley into the alliance in order to get the majority of the vote.
The Tribe Shuffle
On Day 10, both tribes were shuffled by a Schoolyard Pick and Jacquie was transferred to Fang, separating her from the rest of the alliance who remained on Kota. At the new Fang, Jacquie was targeted by former Kota outcast Kelly Czarnecki, who joined the Fang Alliance. When Fang lost the Immunity Challenge on Day 12, Jacquie was voted out as a threat due to her close relationships to The Onion Alliance.
Despite the loss of an original member, the swap gave the Kota tribe three new members from the Fang tribe: Susie Smith, Randy Bailey, and Dan Kay. Because of his strength in challenges, Randy earned respect from the tribe and was invited into the alliance. Dan also tried to join the alliance but was unsuccessful.
When both Kota and Fang had to go to Tribal Council on Day 21, the alliance had to pick between the two outsiders: Susie and Dan. Because of the possibility that Dan had the Hidden Immunity Idol, they decided to keep Susie, and they voted out Dan. This proved to be fatal as Susie flipped to the Fang Alliance.
The Second Tribe Shuffle
The day after the double Tribal Council, both tribes were invited to a feast which they assumed was the merge feast. During the feast, Ken Hoang from Fang tribe spotted a clue to the Hidden Immunity Idol, but Charlie also saw it and decided to share the clue with everyone. Soon, the Hidden Immunity Idol was discovered. However, Marcus and Randy (who worry about the Hidden Immunity Idol may negatively affect the alliance), suggested it to be thrown into the ocean to ensure a "fair" game. Surprisingly, no one objected and the Idol was discarded.
After the feast, the remaining 10 castaways were surprised by a new tribe swap. The new Kota tribe included: Marcus, Bob, Susie, Ken, and Crystal Cox. The new Fang tribe included: Randy, Corinne, Charlie, Matty Whitmore, and Sugar Kiper. Both tribes had old Kota members as the majority. At the new Fang, the Onion Alliance stick together and plan to vote out Matty as a physical threat. At the new Kota tribe, Marcus found out that Crystal is the cousin of one of his best friends, he then formed a secret alliance with her.
When Kota lost the Immunity Challenge on Day 24, Marcus immediately targeted Ken for his intelligence. To ensure that Susie wouldn't flip, he promised to take her to the Final Three along with Charlie. Trusting that Crystal was now a part of the alliance, Marcus tried to convince her to vote against her old tribe mate Ken. However, his plan was backfired when Crystal decided to stay loyal to her alliance with Ken and target Marcus. Crystal then convinced Susie to jump ship and at Tribal Council, Marcus was voted out. The alliance had just lost its leader.
Snake Without a Head
With their leader, Marcus, voted out, the alliance felt vulnerable. The merge eventually came on Day 27 and the Onion Alliance entered the merge in the minority. They tried to convince Sugar to side with them and vote out Crystal. Meanwhile, the Fang alliance secretly targeted Charlie as a physical threat. Ultimately, Sugar stuck with her alliance and Charlie was voted out.
When Bob was sent to Exile Island on Day 26, he was not able to find the Hidden Immunity Idol because it had already been found by Sugar, so Bob came up with a plan to fake the idol. After Charlie was voted out, the alliance was going to vote off Bob for being a physical threat. However, Sugar acknowledged the fact that Bob made a fake Hidden Immunity Idol and planned a joke to fool Randy as well as voting him off in the next Tribal Council. Bob agreed with Sugar on the plan and gave the fake idol to Randy. Thinking the idol was real, Randy play it without a doubt. Randy was voted out with most of the tribe laughing at him.
Bob won immunity on Day 33, putting Corinne on the chopping block. Bob made a new Hidden Immunity Idol in attempt to convince Ken and Crystal to jump to their side. The plan was not successful and Corinne was voted out, leaving Bob the last remaining of the onion alliance.
The Last Onion Remaining
Being the last remaining member of the onion alliance, Bob was set to be on the chopping block by default. Amazingly, Bob went on a winning streak, won five challenges in a row and kept himself safe at Tribal Council, forcing the Fang alliance to turn on each other.
Unfortunately, Bob's winning streak come to an end when Susie beat him at the Final Immunity Challenge. Fang alliance member Sugar, who had a strong relationship with Bob, however wanted him to be in the Final Three with her. Sugar told Bob to practice for the tiebreaker challenge and quietly switch her vote to Matty in order to force a tie. Bob won the tiebreaker over Matty and became one of the three finalists to sit at the Final Tribal Council.
At the Final Tribal Council, the Onion Alliance unanimously voted for their only ally in the Final Three. Bob became the winner of Survivor: Gabon by a vote of 4-3-0 over Susie and Sugar respectively.