This is just a short little glimpse into Erik's mind about why he was so angry with Charles for the majority of DOFP.
Mild spoilers for DOFP, but nothing major. You don't need to have watched the movie before reading this.
Excuse any shoddy writing; I wrote this at two o'clock in the morning during finals week and I have yet to go back and edit it.
A Changed Man
Erik watched from afar as Charles and Hank got off the plane. From the way their heads were positioned close together and the wild way Hank was waving his hands, the metal bender assumed they were talking about science. Although it had been over a decade since Erik had spent any length of time around them, he highly doubted Hank could get that wound up over anything else. It was Erik's experience that people rarely changed.
At least, he amended darkly as his gaze fell on Charles, most people didn't.
Rage and frustration once more simmered in his veins as Erik glared at the shaggy, run-down excuse for a man that had once been his closest friend. For the life of him, Erik couldn't even begin to figure out what exactly had happened to Charles. This complete identity change went far beyond abandonment-Erik should know, having been left behind by everyone he had ever cared about.
This was cowardice, and it angered Erik beyond words.
Charles could be called many things, but coward was one word Erik had never dreamed of associating with him. The former telepath was fearless, jumping into the ocean in the middle of the night to rescue a complete stranger, racing after said stranger into a heavily guarded Russian safehouse to once more acts of stupidity, and perhaps the bravest act of all: taking on someone far more powerful and getting shot in the back over principles. While Erik might not have agreed with the acts themselves, he could not deny the bravery that went behind them.
But the man who stood behind Hank now was a man who had given up his powers, who had given up everything that had made him Charles, and it made Erik physically ill to look at him.
The metal walls of the airplane hangar began to vibrate. Erik clenched his hands into fists and forced himself to breathe deeply.
Charles lifted his head, his gaze meeting Erik's. Where there had once been compassion and serenity, now lay only mistrust and pain.
It was the final straw. Erik could handle a lot-deaths of the people he cared about, massive physical injuries, the entire world hunting him for a difference of opinion-but he could not handle his once closest friend turning his back on everything and then blaming Erik entirely for it.
The metal bender turned on his heel and stormed out of the hangar.