Agents of S.H.I.E.L.D. began with the mystery of Coulson's resurrection, and it's only fitting that its 100th episode brings his death. The series kicked off in 2013, and back then it was essentially the Marvel Cinematic Universe's tie-in TV show. It starred Clark Gregg, reprising the role of Agent Phil Coulson - in spite of the fact his character had actually been killed in 2012's The Avengers. Some fans initially believed that meant Agents of S.H.I.E.L.D. would be set before the Marvel movies, but instead it turned out that Coulson had been mysteriously resurrected. Much of seasons 1 and 2 were dedicated to exploring this resurrection.
Now, five seasons on, Agents of S.H.I.E.L.D. is about to celebrate its 100th episode. Unfortunately, there may not be a season 6; ABC actually tried to cancel the series at the end of season 4, but were overruled by Disney. Given that the series' future is uncertain, how should Agents of S.H.I.E.L.D. celebrate its 100th episode? Well, perhaps the best answer is a move that would take the show full-circle: Phil Coulson's death.
Phil Coulson Is Dying
In a shocking twist, the episode "Past Life" saw Coulson stabbed by a rampaging Inhuman berzerker. The scene wasn't really a focal point of the episode, meaning its import was initially missed by fans. At least, until a future version of Yo-Yo revealed that Coulson had taken a fatal injury. A mysterious black toxin - vaguely reminiscent of the Kree-derived toxins used by Hydra in Agents of S.H.I.E.L.D. season 2 - is spreading through his body. According to this future Yo-Yo, the attempt to save Coulson's life is one of the events that leads to the end of the world.
So far, Coulson has kept his injury secret. It's understandable; the S.H.I.E.L.D. team has returned to Earth as the world's most wanted, and already they've detected the "light in the sky" that led to the Kree arrival on Earth. Yo-Yo's injury in "All the Comforts of Home" is a shocking twist, confirming that everything her future self said - and did - was true. Worse still, it suggests that the Earth's destruction is imminent.
Yo-Yo is the only one who knows Coulson is injured. Now, having realized that her future self was telling the truth, she's sure to confront Coulson and force the truth out into the open. Crucially, she also knows that the attempt to save Coulson's life will be a mistake. It's not likely the others will pay close attention to that, but Coulson would certainly listen.
A Thematic Irony
There would be a certain thematic irony in killing Phil Coulson. When Agents of S.H.I.E.L.D. began, it was essentially focused on the mystery of Coulson's resurrection. In fact, the whole team had been put together by Agent May in order to assemble a group who could help if the resurrection went wrong. "I assembled the team," May snapped at Coulson, and explained she'd subtly manipulated him into picking the agents she believed she'd need if he wound up out of control.
The first two seasons continually returned to Coulson's resurrection, gradually revealing he had been brought back to life using Kree blood. When Coulson finally gained an understanding of the T.A.H.I.T.I. project, he wound up suffering from severe psychological effects. These ultimately led S.H.I.E.L.D. to the ancient Inhuman city, launching the Inhumans plot that has continued ever since.
Coulson's death and resurrection dominated the first two seasons of Agents of S.H.I.E.L.D.. They also laid the foundation for everything the series would go on to do. It would be tremendously appropriate for the 100th episode to bring the story full circle, with Phil Coulson dying once again.