4. "What If... Strange Supreme Intervened?" (Season 2, episode 9)
The finale of What If...? season 2 brought two of the show's biggest heroes together and pitted them against each other in a stunning battle that was every bit as tragic as it was jaw-dropping. Captain Carter and Doctor Strange Supreme reunite as the former needs "help" retrieving a lost villain to add to his collection, but what he doesn't reveal is that he is actually using these villains and heroes to bring back his world and ultimately save Christine. The "villain" Carter was to retrieve was Kahhori, who we met in the sixth episode of the season.
While this finale isn't as ambitious as the first season's culmination, the stakes are every bit as high. It felt right that it revolved around Strange, Carter, and Kahhori, as the trio are arguably What If...?'s main characters, and that heightened the tension well, because honestly we didn't know who was going to win.
Speaking of main characters, Captain Carter and Kahhori are the standouts of season 2, so seeing them team up to take down Strange Supreme was out-of-this-world; as was seeing Carter form an armor that boasted the Infinity Stones.
"What If... Strange Supreme Intervened?" throws everything at the wall to see what sticks and I had a heck of a good time watching it do it. It's a bittersweet episode, because Strange ventures down a dark path that he can't return from this time, but the resolution feels like an appropriate culmination to his arc - and the season.