Here is some. Some of this you may want to emit with little or no ties to the X-Men but i notice you have a few mutants on the list with no ties to X-Men. Take and leve as you please
Groups
Bio-Genes (Leecher, Mali, Transfaser)
Great Lakes Avengers (Big Bertha (Ashley Crawford/Bertha), Doorman (DeMarr Davis), Flatman (Matt/Val Ventura))
Morlocks (Electric Eve, Litterbug)
Thunderiders (Cowboy (Luke Meriweather), Honcho (James McDonald), R.U. Reddy (Winthrop Roan, Jr.), Wolf, Wrench (Leonard Hebb))
X-Cellent (Hurt John, Mirror Girl, Uno, Venus Dee Milo (Dee Milo), Zeitgeist (Axel Cluney)
X-Statix (The A (Mike Alicar), Dead Girl (Moonbeam), Doop, Mister Sensitive (Guy Smith), Phatty, Vivisector (Myles Alfred)
Active and powered
Base (Hiro Sokuto), Blacklung the Malady Man (Tristram Oberbeck), Burn (Bethany Bellamy), Catiana (Tatiana Caban), Crazy Maise, Danger (Dolph Dongen), Dead Ringer (Louis "Lou" Dexter), Doctor Goodwrench, Forever Man, Goblyn (Dean), Grip (Brandon Blake), Humus Sapien (Sonny Baredo), Ill Billy (William Williams), Jolt (Kyi), Jonathon White, Katie Sawyer, Klara Prast, Manikin (Whitman Knapp), Manslaughter, Mindblast (Danielle Forte), Molly Hayes (Bruiser), Noise (Julio Mendoza), Outlaw (Inez Temple), Pathway (Laura Dean), Pete Gehringer, Picaro (Antonio Rey), Powerhouse [Spider-Man foe], Puff Adder (Gordon Fraley), Purple Woman (Kara Killgrave), Quagmire-712 (Jerome Myers), Robin Vega, Sirocco, Snake Whip (Leeann Foreman), Stealth (Carlos McNally), Streetman, Suede (Nicholas Blake), Tattoo (Tudo Sokuto), Teleplex, Threnody (Melody Jacobs), Topspin (Darren Mitchell), Typhoid Mary (Mary Walker), Zapper (Colin Smith)
Earth-616 per the Handbooks
Cascade (Ross Kinkaid), Eye-Scream, Roger Fieldston
Depowered but still active in their costume identites
el Aguila (Alejandro Montoya), Bloodlust (Beatta Dubiel), Brass (Sean Watanabe), Johnny Justice (Jonadab Megyscol), Orange Crusher (Andy Gardner), Razorback (Buford T. Hollis)
Deceased
Adrian Leverkuhn Castorp, Aminedi, la Bandera, Blowtorch Brand (Peter Brand), Blue Condor (Emilie Scholz), Centennial (Rutherford B. Princeton III), Critical Mass (Arnie Gunderson), Gibbon (Martin " Marty" Blank), Goldfire (Ameiko Sabuki), Gremlin/Titanium Man (Kondrati Yurivich Topolov), Half-Mad, Joe Bugs, Mastermind (Jason Wyngarde) Mindworm (William Turner), Mister Density (Gus Yaccarino), Mister One and Mister Two, Plasma (Leila O'Toole), Quickstar (Robert Nazaro), Ricochet (Steven Shaffran), Roman Candle (Armand Galante), Shockjock (Kenneth Sjolin), Sister Salvation, Solarr (Silas King), Tick Tock, Willie Evans, Jr.