Okay, i have a cherik prompt. Let me set the scene.
A universe where they do end up as rivals, distant but still respect one another, old friends. The og timeline if you will.
Close enough to touch but just far apart to feel the searing pain of betrayal as well as the heartbreaking pride to stay true to their beliefs.
Erik is at the Mansion unbeknownst to the students. Charles and him share a game of chess, maybe a glass of wine. Erik's reason for being there, maybe it's to politely warn Charles of an upcoming mutant villain (to warn Charles to stay out of his way of course.) or perhaps he's injured. Or maybe he was just craving some company.
They share a sweet moment together but after, Erik breathlessly whispers
"I've missed you Charles."
Charles pauses and huffs before responding.
"i miss you too, old friend"
Do with that what you will