Tokusatsu trios! Mr Holmes!

Ultraman Omega

It's his name and also he grows taller than skyscrapers thus he is. the biggest omega. 

Broke all of his people's laws for love, even after remembering his past. And he looks so cool doing it.

Dean Winchester

One big draw of omega verse fanfiction is to play with gendered expectations and their horrors in an exaggerated way/heightened in a way that it feels less real and easier to approach (also its hot, lets not forget that), Dean in canon struggles a lot with binding his self worth to a limited view of masculinity while also having a connection to things he views as female; he is often pushed in the caretaker role toward his younger brother and while he genuine enjoys some of it, the lack of choice is always a thorny aspect. Dean Winchester would hate being an omega, and torturing him is something canon (and fanon) loves to do.