Merging (humanoids) – The merging of two or more humanoids.
Agent Axis (Marvel) was created when a German, Italian and Japanese agent merged into one person (Annual Invaders V1 #1).
In Superboy and the Legion of Super-Heroes #234, radioactive deposits cause four of the Legionnaires, Colossal Boy, Shrinking Violet, Saturn Girl and Lightning Lad, to amalgamate into the Composite Legionnaire.
Mangog was created by the merging of a billion, billion, humanoids by Odin in Thor V1 #157.
The Overmind (Marvel) is a billion alien Eternals merged into one mind.
Starro merges humans forcibly (Justice League of America V1 #190).
Tuvik was created when Tuvok and Neelix were merged in Star Trek Voyager, Season 2, Episode 24.
The Ubersaur is a merged being used as a weapon (Astro City #30, 2016).
The Uni-Mind (Marvel) is created by the merging of Eternals.
In The Chimera Brigade (Titan), a group of mad scientists that rule Moscow claim that “there exists but one superman, invisible, collective, and immortal: the human species itself.”
The Collective Man (Marvel) consists of five brothers who can fuse into one being and use their power to defend China (Official Handbook of the Marvel Universe V1 #2).
Chaos is a community organism that absorbs humans in order to gain power Pantheon #8 (Lone Star Press).
Black Magic V2 #1 (DC)
Ermac – Mortal Kombat 9 (2011) Prima Guide
Legion of One – Creature Collection II. Dark Menagerie
Mongrelman – TSR 2140A Monstrous Manual
Theodore Sturgeon’s More than Human – Heavy Metal (1978)
Varua (Marvel) can make a Uni-mind with none eternals (Spectacular Spider-Man Annual V1 #8).
Warstar (Marvel) consists of two symbiotically linked mechanoids in Avengers West #80.
The very interesting one-shot merged human known as the X-Man (Marvel) in What If V1 #2 that should be not be confused with the other X-Man (Marvel) that is a million times more famous.
Deathstroke (DC) and Wonder Woman (DC) face a demonic, one-shot, merged humanoid in Tartarus (Annual Deathstroke V3 #1).
One of the Dark Gods can forcibly absorb innocent humans in Evil Dead 2 Dark Ones Rising #2 (Space Goat Publishing).
A comparison of comic book characters with this power at Comic Book Merged Humans.