Mutant Levels

[Eros]

List is in order from Greatest and most powerful to the lessened and most flawed.

O
[×] Omega level mutants‎
A
[×] Alpha Level Mutant‎
B
[×] Beta-level Mutant‎
D
[×] Delta Level mutant‎=Make up 50% of the mutant population
G
[×] Gamma-Level mutant‎
E
[×] Epsilon Level Mutant‎

[Eros]

Alpha-A

The Alpha Mutants are the second most powerful and feared mutants. Alpha mutants have extremely powerful mutant traits without any significant flaws. Less than 10% of mutants are Alpha mutants so they are very rare. Some of the Alpha mutants included Gambit, Psylocke, Banshee, Colossus, and Cable.
Classify Mutants as Alpha level if they have a normal human appearance and their mutation is powerful, useful and controllable (i.e. turn it on and off, direct it at will.)


Beta-B

As far as how potent their powers are Beta Mutants are on the same level as Alpha-level mutants. But the difference between Beta Mutants and Alpha Mutants is that the Beta Mutants have flaws, albeit very small flaws. The Beta mutants are also believed to be about 10% of the mutant population. Some examples of Beta mutants are Cyclops and Wolverine.
Classify mutants as Beta Level if they have a normal human appearance (or close to it) and their mutation is powerful, useful, but less controllable, like Cyclops who can't willingly turn off his optic blasts, but can still lead a normal life with only minor preparation (wearing special glasses). Wolverine, who has healing powers, can't ever decide NOT to rapidly heal from an injury, but this does not impair him in any reasonable way.

Delta-D

Delta Mutants are like Alpha mutants in that they don't have any significant flaws. The only problem is that Delta mutants don't have powers that match an Alpha mutant, or even a Beta or Gamma mutant. At least 50% of mutants are Delta mutants making them the most common type of mutant.
Classify mutants as Delta-Level if they have a normal human appearance, but their mutagenic powers are weaker or only narrowly applicable, though still controllable.

Epsilon-E

Epsilon Mutants are unfortunate mutants. Epsilon mutants pretty much have no chance of having a regular life in society due to their major flaws. If that isn't bad enough Epsilon mutants also only have minor superhuman powers. About 20% of mutants are Epsilon Mutants. A good example of an Epsilon mutant is Beak.
Classify mutants as Episilon Level if they have an inhuman appearance or their mutation makes it impossible for them to function normally. Any accompanying "superpowers" would be next to useless. Epsilon mutants are differentiated from Gamma mutants in that a Gamma mutant's inhuman appearance would provide a compensating benefit like superior strength.


Gamma-G

Gamma mutants have very powerful mutations, but they have flaws. Unlike the Beta mutants a Gamma mutant's flaw is a major flaw that makes his or her life very hard. The best example is probably Rogue. Rogue can absorb anybody's power, which makes her very powerful, but she can't touch people without triggering her power, which makes any kind of romantic life difficult. Also, while Alpha and Beta mutants can pass as regular looking humans, many Gamma mutants cannot because they have physical deformities like Blob or Marrow.
Classify mutants as Gamma Level if their mutation is powerful, uncontrollable, sometimes useful but usually detrimental to living a normal life, such as a monstrously inhuman appearance that can't be switched off at will.

Omega-O

The terms "Alpha" and "Omega" (roughly meaning "first" resp. "final") are blurry in-universe terms used by some writers to categorise different characters. Omega mutants are, in theory, supposed to be the most powerful class of mutants, but with time the scope of the term has widened to include a much wider scope of characters that, following the same logic, could technically qualify half the ones in existence.
Originally omega mutants were beings with vast control over matter and energy, such as Iceman, Phoenix, Legion.

The term "Alpha mutant" can, but does not necessarily, intersect, but the distinction is usually blurry, and varies depending on the writer. Jean Grey is sometimes considered an "Alpha" because of her type of power, and lack of flaws, whereas Gambit is sometimes also considered as an alpha, but not as powerful enough to be an "Omega".