X (misc.)

X-Terminators (1988-1989)

Gambit and the X-Ternals (Age of Apocalypse) (1995)
X-Calibre (Age of Apocalypse) (1995)
X-Universe (Age of Apocalypse) (1995)
X-Nation 2099 (1996)
X-Patrol (Amalgam) (1996)
The Exciting X-Patrol (Amalgam) (1997)

X-Necrosha (2009)

X-Necrosha: The Gathering (2010)

X-Campus (2010)

X-Women (2010)

X-Club (2012)

X-Termination (2013)

X-Tinction Agenda (2015)

Death of X (2016-2017)

See also:
X-Infernus