Frightening Four

Can also be the Frightening Five, Fourteen, Fifteen, or others. Also sometimes called the Frightening Foes.

Easily defeated the Frightful Four.

Frightening Four First Version
Mister Hyde (Leader)

Grim Reaper

Tiger Shark

Jack-O-Lantern

Frightening Five First Version
Mister Hyde (Leader)

Grim Reaper

Tiger Shark

Jack-O-Lantern

Swarm or Mister Fear

Frightening Five Second Version
Later on after the Frightful Fourteen

Mister Hyde (Leader)

Tiger Shark

Scarecrow

Swarm

Vengeance

Frightening Fourteen
Mister Hyde (Leader)

Grim Reaper

Tiger Shark

Man-Bull

Swarm

Mister Fear (Alan Fagan or Larry Cranston)

Living Laser

Hobgoblin or Jack-O-Lantern

Griffin

Madcap

Brothers Grimm Squid
 * Percy Grimes
 * Barton Grimes

Frightening Fifteen
Mister Hyde (Leader)

Tiger Shark

Hobgoblin or Jack-O-Lantern

Scarecrow

Swarm

Vengeance

Human Fly

Vermin

Armadillo

Frightening Foes / Frightening Fifteen Second Version
Mister Fear (Leader)

Jack-O-Lantern or Hobgoblin

Orb

Swarm

Monster

Plantman (Samuel Smithers)

Lobo Brothers Iguana
 * Carlos Lobo
 * Eduardo Lobo

Harpy

Morgan Le Fey's Frightening Legion
Morgan Le Fey (Leader)

Chernobog

Vlad Dracula

All Members - Any Combination

 * 1) Mister Hyde (Always leader when on the team)
 * 2) Grim Reaper
 * 3) Tiger Shark
 * 4) Man-Bull
 * 5) Swarm
 * 6) Mister Fear (Alan Fagan or Larry Cranston) (Leader when Mister Hyde is not on the team)
 * 7) Living Laser
 * 8) Hobgoblin
 * 9) Griffin
 * 10) Madcap
 * 11) Brothers Grimm - Percy Grimes
 * 12) Brothers Grimm - Barton Grimes
 * 13) Squid
 * 14) Scarecrow
 * 15) Vengeance
 * 16) Orb
 * 17) Monster
 * 18) Jack-O-Lantern
 * 19) Plantman (Samuel Smithers)
 * 20) Black Talon
 * 21) Doctor Demonicus / Demonicus
 * 22) Vermin
 * 23) Death-Stalker
 * 24) Lobo Brothers - Carlos Lobo
 * 25) Lobo Brothers - Eduardo Lobo
 * 26) Iguana
 * 27) Harpy
 * 28) Ranark the Ravager
 * 29) Morgan Le Fey
 * 30) Chernobog
 * 31) Wendigo
 * 32) Freak
 * 33) Vlad Dracula
 * 34) Human Fly
 * 35) Armadillo

Maybe
Purple Man?

Purple Woman?

Dr. Cornelius (Ultimate universe version)?

Red Ghost?

Carnage?

Hydro-Man?

Mysterio?

Reptilla?

Constrictor?

Mandrill?

Jonas Harrow?

Abomination?

Bi-Beast?

Icemaster?

Morg?

Mudbug?

Cullen Bloodstone / Glartrox?

Grey Gargoyle?

Nightshade?

Chimera?

Dansen Macabre?

Dragon Man (Before becoming good)?

Hippo?

Lizard?

Morbius (Before becoming good)?

Skein?

Will O' The Wisp?

Firebrand (Either version)?

Machinesmith?

Blackwing?

Deathwatch?

Thousand?

Menace?

Dragonclaw?

Tombstone?

Man-Wolf?

Goblin King?