Many characters in the Marvel and DC universes have so much in common that it is hard to believe that the latter wasn't inspired by the former. The following characters have astonishingly similar personalities despite being in separate universes.
Ant-Man (Marvel)/Atom (DC)
Both Dr. Hank Pym and Dr. Ray Palmer have the ability to shrink their size. They are one of the most highly regarded scientific geniuses of their respective universes.
Aquaman (DC)/Namor (Marvel)
Probably everyone knows the obvious similarities between these characters. Both of them have human fathers and Antlantean mothers. Both royalties have obligations to Atlantis. Their powers are also almost identical too, like extremely rigid skin except Namor can't communicate with aquatic life whereas Aquaman can't fly.
Black Lightning (DC)/Electro (Marvel)
The characters can generate strong magnetic fields and discharge electricity through their bodies. The magnetic field generation allows Black Lightning to fly. Other similar powers are electric projection, electric absorption, electric form, etc.
Captain America (Marvel)/Commander Steel (DC)
Captain America has enhanced physiology due to experimentation. Similarly, an enhanced surgery was carried out on Commander Steel that increased his physical strength, speed and durability through mechanized steel devices. Like Steve Rogers, he took part in World War II.
Catwoman (DC)/Black Cat (Marvel)
Catwoman and B
lack Cat are both excellent thieves and combatants who can be considered as anti-heroes. Not to mention they have very similar names and costumes.
Clayface (DC)/Sandman (Marvel)
Both these characters can manipulate sand and change their size, shape and density at will. Thus, their defining powers are largely the same.
Darkseid (DC)/Thanos (Marvel)
Thanos and Darkseid are considered two of the most powerful characters of their respective universes having various supreme powers like superhuman strength, flight, teleportation, energy manipulation/control and telepathy.
Hawkman (DC)/Angel (Marvel)
Having the ability of flight due to their vast angelic wings, Hawkman and Angel can be considered quite similar. They have a strong healing factor as well.
Green Lantern (DC)/Quasar (Marvel)
Pretty much similar to the way Green Lantern uses his ring to make various constructions with his mind, Quasar uses the bands on both of his hands to make melee weapons. Quasar is a normal human being without his bands like Lantern is without his rings.
Green Arrow (DC)/Hawkeye (Marvel)
This one's staggeringly obvious. Both Arrow and Hawkeye use a bow and arrows as their primary weapon. They have wide variety of arrows that allow them to do various functions. Both of them lost their parents in childhood.
Ghost Rider (Marvel)/Atomic Skull (DC)
Although Ghost Rider has a much wider range of abilities like demonic transformation, mystical chain projection and penance stare, their common traits include energy projection, superhuman strength, stamina and durability.
Quicksilver (Marvel)/Flash (DC)
The Flash was the original speedster which was followed by the mutant Quicksilver. They have the same set of powers but are at a different scale. In terms of speed, Flash exceeds Quicksilver to a great extent.
Dr. Polaris (DC)/Magneto (Marvel)
Both have virtually the same set of powers that include control over magnetic fields and metal. They were both created in 1963. Magneto has a daughter named Polaris that can control metal too.
Doctor Fate (DC)/Doctor Strange (Marvel)
The doctors are extremely powerful magicians of their universes who have the ability to flight and innumerable magical abilities. Their powers were given to them by another supreme sorcerer.
Deadpool (Marvel)/Deathstroke (DC)
No doubt Deadpool a.k.a. Wade Wilson was inspired by Deathstroke a.k.a. Slade Wilson. They share surprisingly similar qualities like superhuman healing. Their wide range of weapons include guns and explosives, but prefer their dual blades over them. And if that wasn't enough, the anti-heroes have very similar costumes.
Hulk (Marvel)/Grundy (DC)
Bruce Banner transforms into an enormous beast known as the Hulk when he's angry since his exposure to gamma radiation. He has superhuman strength and durability that increases with his anger. Grundy too, has enormous superhuman strength and stamina. Also, both of them have diminished intellect.
Martian Manhunter (DC)/Vision (Marvel)
Their in-common abilities include genius-level intellect, intangibility, enhanced strength and durability, cell generation, density manipulation and flight. However, Manhunter has a load of other abilities as well.
Moon Knight (Marvel)/Batman (DC)
Moon Knight is highly comparable to Batman due to his mega rich personality and his urge to fight crime at night using weaponry and gadgets. He is an elite fighter and his costume is quite similar to that of Batman.
Mr. Fantastic (Marvel)/Elongated Man (DC)/Plastic Man (DC)
In my opinion, the similarities between all three speak for themselves. Both Reed Richards and Elongated Man were followed by the original Plastic Man. They can stretch their body according to their will which makes them nearly indestructible.
Gladiator (Marvel)/Superman (DC)/Hyperion (Marvel)
All three share almost the same combination of powers like superhuman strength and flight. Furthermore, Hyperion was a baby that was sent from a dying world and was raised by ordinary folks who instilled him with a strong sense of morality. Sounds pretty familiar, right?
Swamp Thing (DC)/Man-Thing (Marvel)
Swamp Thing and Man-Thing are virtually the same character despite minor differences. It's not sure which came first but it can be said that both were inspired by The Heap which was created in 1942.
Ultron (Marvel)/Braniac (DC)
Both highly intelligent automations can make and control their clones and other machines as well. They can self-repair and are immensely skilled fighters.
Wasp (Marvel)/Bumblebee (DC)
The Wasp and Bumblebee gained their powers through advanced science. Despite the fact that Bumblebee is stuck with her tiny size and Wasp can change her size at will, their are any visual and intrinsic parallels between the two.
Source: via 9gag