Marvel
| Name | Super Name | Code | Actions |
|---|---|---|---|
| Onyxx | Onyxx | Onyxx | Show |
| Onslaught | Onslaught | Onslau… | Show |
| Omega the Unknown | Omega the Unknown | Omega-… | Show |
| Omega Red | Omega Red | Omega-… | Show |
| Omega Clan | Omega Clan | Omega-… | Show |
| Omega | Omega | Omega | Show |
| Olivier | Olivier | Olivier | Show |
| Old Lace | Old Lace | Old-La… | Show |
| Ogun | Ogun | Ogun | Show |
| Ogress | Ogress | Ogress | Show |
| Ogre | Ogre | Ogre | Show |
| Oddball | Oddball | Oddball | Show |
| Occulus | Occulus | Occulus | Show |
| Obliterator | Obliterator | Oblite… | Show |
| Nuklo | Nuklo | Nuklo | Show |
| Nuke | Nuke | Nuke | Show |
| Nuke (Squadron Supreme) | Nuke | Nuke-S… | Show |
| Nth Man | Nth Man | Nth-Man | Show |
| Nova (Richard Rider) | Nova | Nova-R… | Show |
| Nova (Frankie Raye) | Nova | Nova-F… | Show |