Doctor Doom

Few villains in Marvel's pantheon cast as long a shadow as Doctor Doom, and this incarnation stepped onto the page in Jim Krueger and Alex Ross's visionary Earth X in 1997 — a prestige project that immediately signaled his key-issue importance. Over nearly three decades, this version of the armored sovereign of Latveria has kept remarkable company, sharing adventures with the likes of Captain America, Spider-Man, and Reed Richards across a diverse run of Marvel titles. His appearances in series like Amazing Spider-Man by Zeb Wells and Amazing X-Men speak to a character whose brooding, imperious presence fits naturally into almost any corner of the Marvel universe. Sixteen catalog appearances across 28 years may be a selective footprint, but for a character with Doom's gravity, every single one counts.