Looking at (14912-1491)/2 = 1,110,795 comic book character co-occurrences (two characters showing up in the same comic) across the history of Marvel Comics. A subset of this visualization - just the Top 100 characters - can be viewed here.
Code for this chart is on github, and a description of the impetus to this project is on Medium. This visualization is based on Mike Bostock's Les Misérables co-occurrence matrix diagram. Data provided by Marvel © 2018 MARVEL via Marvel Developer.
Comments and suggestions are welcome on github, Medium, or here. Note: I've intentionally not shared the cached data pulled from Marvel Developer, only the directed graph data to build this visualization.