5* feeders / 4* champ rewards (full list)

HoundofShadow

Archangel

Black Bolt ———————————— Medusa

Black Panther —————————— Black Panther

Black Widow ——————————— Black Widow

Cable

Captain America (First Avenger) —— Peggy Carter

Captain America (IW) ——————— Winter Soldier

Captain Marvel —————————— Captain Marvel

Daredevil ————————————— Kingpin

Doctor Doom

Doctor Octopus —————————— Carnage

Doctor Strange —————————— Mordo

Gambit

Ghost Rider ———————————— Ghost Rider

Green Goblin ——————————— Sandman

Hawkeye ————————————— Kate Bishop

Hela

Iceman

Iron Man ————————————— War Machine

Jean Grey ———————————— Jubilee

Jessica Jones ——————————— America Chavez

Kingpin —————————— Miles Morales

Kitty Pryde

Loki ———————————————The Hulk (Main Event)

Okoye —————————————— Shuri

Prof X

Rescue

Silver Surfer ———————————— Mr. Fantastic

Spider-Man (Back in Black) ————— Spider-Man (Infinity War)

Spider-Man (Peter Parker) ————— Vulture

Star-Lord ————————————— Drax

Storm 

Thanos —————————————— Gamora

The Hulk

Thor ——————————————— Valkyrie

Wasp ——————————————— Ant-Man

Wolverine ————————————— Wolverine

Note: 37 5-star characters. 11 5-stars don't have feeders yet.

turianbrandy

They're taking waaaay too long to update/complete this on the devs end.

4*Deadpool should give Cable

4*Cyclops should give Prof X

Coulson should give Rescue

Rogue should give Gambit

4*Iceman should give 5*Iceman

Domino should give Archangel

Hulkbuster should give Hulk

Invisible Woman should give Doom

Magik should give Kitty Pryde

Jane Foster should give Hela
Nightcrawler should give Storm

Zzzz what gives devs...

111MCH111

With the introduction of shards, all your questions are answered. Differently, example: Emma Frost feeds Kitty

HoundofShadow

Thanks for bumping this post. However, it has not being updated for more than 2 years. Let me see if I can help to update it.

Edit: time flies. The last time I updated it, there was 37 5*. Now, there's 62.

HoundofShadow

Updated till: 5* Riri Williams (Ironheart 3.0) and Thanksgiving 

Abigail Brand (Commander of S.W.O.R.D.) -

Adam Warlock (Infinity Watch) - Mantis

Apocalypse (Classic) - Beast (AoA)

Arcade (Edward Acra) - MODOK

Archangel (Classic) - Nightcrawler

Beta Ray Bill (Korbinite Cyborg) - Throg

Big Wheel (Jackson Weele) -

Black Bolt (Inhuman King) - Medusa

Black Panther (Civil War) - Black Panther

Black Widow (Natasha Romanoff) - Black Widow

Cable (Nathan Summers) - Bishop

Captain America (First Avenger) - Peggy Carter

Captain America (Infinity War) - Winter Soldier

Captain Marvel (Galactic Warrior) - Captain Marvel

Carnage (Prophet of Knull) - Scorpio

Chasm (Ben Reilly) -

Colossus (Phoenix Five) - Puck (Eugene Judd)

Cyclops (Phoenix Five) - Echo (Maya Lopez) + Cyclops

Crystal (Crystalia Amaquelin) -

Daredevil (Matt Murdock) - Kingpin

Deadpool (Spirit of Vengeance) - Spider-Man (Oscorp) 

Doctor Doom (God Emperor) - Invisible Woman

Doctor Octopus (Classic) - Carnage

Doctor Strange (Sorcerer Supreme) - Mordo

Electro (Francine Frye) - Doc Ock (No Way Home)

Elektra (Woman Without Fear) -

Emma Frost (Phoenix Five) - Emma Frost

Gambit (Classic) - Rogue

Gamora (Deadliest Woman) -

Gargantos (Multiverse of Madness) -

Ghost Rider (Robbie Reyes) - Ghost Rider

Green Goblin (Norman Osborn) - Sandman

Havok (Classic) - Reptil (Humberto Lopez)

Hawkeye (Clint Barton) - Kate Bishop

Heimdall (The Gatekeeper) - Loki-gator

Hela (Goddess of Death) - Magik

Iceman (Bobby Drake) - Iceman

Iron Man (Mark XLVI) - War Machine

Jean Grey (Phoenix) - Jean Grey

Jessica Jones (Alias Investigations) - America Chavez

Kamala Khan (Origin) - Lockjaw

Killmonger (Erik Stevens) - Hydra Stomper

Kingpin (Spider-Verse) - Miles Morales

Kitty Pryde (Uncanny X-Men) - Kate Pryde & Doop

Knull (King in Black) - Rhino (Classic)

Loki (God of Mischief) - Main Event Hulk

Magneto (Age of Apocalypse) - Juggernaut

Mister Sinister (Nathaniel Essex) - Blob

Moon Knight (Avatar of Khonshu) -

Odin (All-Father) - Namor

Okoye (Warrior General) - Shuri

Onslaught (Psionic Entity) - Gorr (The God Butcher)

Professor X (Classic) - Prof. X

Rescue (Pepper Potts) - Iron Man (Hulkbuster)

Riri Williams (Ironheart 3.0) - Riri Williams

Ronan (The Accuser) -

Scarlet Witch (WandaVision) - Hulkling (Dorrek VIII)

Sersi (Eternals) -

Shang-Chi (Origin) -

She-Hulk (Immortal): She-Hulk (Origin) 

Silver Surfer (Skyrider) - Mr Fantastic

Spider-Man (Back in Black) - Spider-Man (Infinity War)

Spider-Man (Peter Parker) - Vulture

Star-Lord (Awesome Mix Volume 2) - Drax

Storm (Ororo Munroe) - Thor (Goddess of Thunder) + Dazzler

Thanos (The Mad Titan) - Gamora

The Hulk (Bruce Banner) - The Hulk (Totally Awesome)

The Hulk (Immortal) - Ikaris

Thor (Gladiator) - Valkyrie

Thor (Mighty Thor) -

Ultron (Age of Ultron) - Gertrude Yorkes (Runaways)

Wasp (Hope Van Dyne) - Wasp

Wolverine (Old Man Logan) -Wolverine (X-Force)

Wolverine (Samurai Daken) - X-23

Yelena Belova (Black Widow) - Red Guardian

Yellow Jacket (Darren Cross) - Ant-Man