MCU: 10 Cosmic Villains For Phase 4
2. The Phoenix Force
The Phoenix Force is a cosmic being of immense power that believes its mission is to ensure the cycle of destruction and rebirth continues and due to this, has been responsible for countless deaths across the universe.
Most of the time, The Phoenix Force requires a host and is most commonly associated with using Jean Grey as its host of choice. While some hosts are able to use the immense power for good, it never usually lasts long as The Phoenix Force's agenda will always overcome their intentions eventually.
The Phoenix Force could trigger a crossover story on an even bigger scale than Infinity War in terms of characters on-screen. In the comics, Tony Stark botches an attempt to repel The Phoenix Force and as a result it splits into five parts and occupies several X-men, this is the foundation of the Avengers Vs. X-men storyline.
Not only could the MCU have all of its active Avengers present, but the inclusion of an entire X-men roster and supporting cast would be monumental. Due to the manner in which The Phoenix Force operates, it's approach could be teased over several movies and hints could be planted all over the galaxy. This would be the most dramatic way to introduce the X-men to the MCU.