Sam Guthrie belongs to the X-Men family along with his sister, Paige (aka Husk).

X-Men.

Who is this?

In the comics, Doctor Voodoo, aka Jericho Drumm, becomes Sorceror Supreme when Doctor Strange loses the spot for using dark magic.

Hero.  No notable team affiliation.

Danny Rand is the Immortal Iron Fist (even though he's not immortal).  Sorta like Kwai-Chang Caine meets the Avengers.

Hint: the Defenders.  Former home: K'un Lun.

Emil Blonsky was exposed to gamma rays with similar results to those that turned Bruce Banner into the Hulk.

Hint: This guys alter ego is Emil.  Wait... Really?  THIS guy is Emil?

Amora has gone by several names, but Enchantress is the one she's best known by.

Hint: Asgardian villain.

Electra Natchios was daughter of a Greek diplomat, became an expert martial artist and assassin... and lover of Matt Murdock/Daredevil.

Hint: Daredevil.

Piotr Rasputin is brother to Illyana/Magik, another powerful mutant.  Sometimes, it runs in the family.

Hint: Magik.  Deadpool movies.

Dr Otto Octavius is one of the classic Spider-Man foes, and Marvel even gave him a stint as the "Superior Spider-Man".  Does changing the adjective actually make it a different character?

Really?  You need a hint?

If you don't get this one, Samuel L. Jackson is going to be very disappointed.

Nope.  Don't even ask.

Easy one... Who is this?

Alien lesbian superhero.  And her parents were soap opera actors... and supervillains.  Then again, those last two are kinda similar.

Hint: Runaways.

Okay... you can't be a Marvel fan and not know this one.

Raven Darkholme has been retooled a couple of times in the MCU via Rebecca Romijn and Jennifer Lawrence.

Hint: Brotherhood of Evil Mutants.

Points to MCU by casting a black actor as a Norse god and getting away with it.

Hint: Idris Elba goes Asgardian

Carol Danvers has had several names.  When wearing the black with gold lightning bolt, she was Ms. Marvel, not Captain.

Hint: different uniform than in the movies.

"Mechanized Organism Designed Only for Killing" has been the head of AIM and foe of several Marvel supers.

In the Netflix series, they used Cage's superhero name as a joke... "Power Man".  I understand the need.

Hint: born Carl Lucas.

Hyperion is another hero who has been killed off and then resurrected by Marvel, in his case in fighting the Beyonders.

Hint: more obscure Marvel hero.  Eternal.  Marcus Milton.

Iron Man has been part of the Marvel media empire for 60 years now, and the Avengers MCU franchise has made him one of the most recognized.

Okay... it's a gimme.

Detective Misty Knight lost her arm in a bomb blast (in the comics) and got her bionic replacement from either Tony Stark (again comics) or through Danny Rand (Netflix series). 

Hint: former detective.  Luke Cage/Iron Fist ally.

Eric Lehnsher has long been one of the big bads of the X-Men, especially in the movie series.

Hint: former POW.

Nico Minoru is a goth Japanese-American sorceress and de-facto leader of the Runaways (though they don't call themselves that).

Hint: Runaways.  Staff of One.

Odin is the big dog in Asgard, being father of Thor and adoptive father of Loki.  Talk about a some family drama...

Hint: Asgardian.  Anthony Hopkins.

In the comics, Jessica was a classmate of Peter Parker.  Small world, hmm?

Hint: Alias Investigations.

Charles Xavier/Professor X is twin to Cassandra Nova and step-brother to Cain Marko/Juggernaut.  Talk about a messed-up family....

Hint: he did some seriously unprintable things to Deadpool in the second MCU installment.

Agent Phil Coulson has made appearances in several titles in the comics but was a big enough hit in the MCU that he scored himself a series in Agents of SHIELD.

Hint: not a super.  SHIELD.  MCU.

Jonathan Storm is brother to Sue Storm (Invisible Woman) and gained his powers in the same cosmic ray accident.

Hint: Fantastic Four.

Cousin to Black Bolt, Gorgon is a major character in the Inhumans franchise.

Hint: Inhumans.  

Maria Hill is Nick Fury's lieutenant and is probably the most under-appreciated character in the Avengers MCU franchise.

Hint: SHIELD.

Victor von Doom, self-made ruler of Latveria, is usually a foe of the Fantastic Four.

Hint: Latveria.

Hammerhead (full civilian name unknown) has been foe of Doc Ock, Kingpin, and many NYC heroes.

Hint: Maggia villain.  Competition to Kingpin.

Norman Osborn is one of the top Spider-Man foes of all time.

Hint: Oscorp.

Alex Summers, brother to Scott and Gabriel, and member of the X-Men, converts cosmic energy into powerful energy blasts.

Hint: X-Men.

Max Dillon is an original member of the Sinister Six and a kind of human capacitor, absorbing and discharging electricity at will.

Hint: Jamie Foxx?

Originally a German noble who was a major figure in HYDRA, he was redefined for the MCU as a Sokovian out for revenge.

Hint: Captain America foe known for wielding a sword.

Seven MCU movies and a dedicated series have gradually changed Loki from one of the original Marvel supervillains to a multiverse-saving hero.  Tom Hiddleston did that.

Hint: popular villain, but seldom seen in this costume in the MCU.

Stephen Strange... Sorcerer Supreme (for a time)... arrogant... master of the Sanctum Sanctorum in NYC... and played in the MCU by Benedict Cumberbatch.

Hint: neurosurgeon.

Neena Thurmann/Domino is member of X-Force along with Cable.  She was largely overlooked by MCU until the Deadpool franchise revived her.

Hint: luck.

Karl Amadeus Mordo has been a frequent opponent of Doctor Strange and occasional servant of Dormammu.

Hint: sorcerer.

Nathan Summers/Cable is a time-traveling cyborg and son of Scott Summers and Madelyne Pryor.  A very "the ends justify the means" kinda guy.

Hint: future mutant.

Bobby Drake is one of the original X-Men, appearing in the very first X-Men issue in 1963.

Hint: mutant.

Molly Hayes is the youngest of the Runaways, and the strongest.

Hint: Runaway.

An Australian who uses boomerangs... so what do they call him?  Talk about minimum effort...

Hint: codename Outback.

I'd never heard of Paul Duval/Grey Gargoyle until encountering him in Marvel Avengers Alliance.  Still not impressed... (And I just threw Bomb Voyage in for fun since he's not even Marvel or DC.)

Hint: French chemist with no specific team affiliation.  Occasional ally of Dr Doom.

Illyana Rasputin/Magik is Marvel's de-facto ruler of Limbo and a student of Doctor Strange (at least in the comics)

Hint: Limbo.

Norbert Ebersol/Fixer sounds more like an accountant than a techno-villain, but no more than probably half of Marvel's bad guys.

Hint: tech genius bad guy.

Hercules, son of Zeus, God of Strength, and heavily foreshadowed as Thor's next opponent in the MCU.

Hint: Olympian immortal.

Skurge is best known as henchman to the Enchantress and foe of Thor.  Karl Urban played him in the MCU, but as Hela's lackey.

Hint: Asgardian.

Lucas Bishop is from another universe from most of classic X-Men but is a still major figure in the franchise.  That makes him a good character.

Hint: time traveler.

Frederick Dukes/Blob is a long-standing henchman of Magneto and the Brotherhood of Evil Mutants.

Hint: Fred.  Magneto ally.

I am eagerly waiting for the MCU to introduce Beta Ray Bill to the masses.  The opportunities for comedy opposite Thor are much better than with the Odinnson as a Guardian of the Galaxy.

Hint: pinch hitter for Thor.

Avengers... X-Men... Fantastic Four... Guardians of the Galaxy... the Defenders... heroes... villains... popular... obscure... all of them!  Images are taken from a defunct Marvel online game and so might be considered "official".