Actually Ryuko and Shadow have a lot of thematic connections
On edge protagonist known for being rather brash and foul mouthed.
Black haired with a prominent red streak.
Created by a mad scientist with plans on destroying the planet.
Was partially made with DNA from the oldest member of an evil alien race.
Gains extraordinarily superhuman abilities from their origins.
Wears a ring around their wrist in order to control their power.
Despite having superhuman speed, often likes to ride a motorcycle.
Prefers fighting with a weapon but is still a master at hand to hand combat.
They're out for vengenance after a loved one of theirs was murdered.
It's later revealed that they and their loved one has a connection with the mad scientist.
Their loved one even used to have a very loving relationship with the scientist.
Along the way they fight a cocky fighter known for his speed, an extremely strong muscle head who's dedicated to being a guardian, a meek technological genius that hates to fight physically, and a pink haired girl with an obsessive crush on someone.
Eventually they become allies with the one person they spent the entire series rivaling, and teams up with that opponent to stop the mad scientist.
Mad scientist attaches another alien life form to a satellite to destroy the earth.
Protagonist undergoes a yellow haired, red aura ultimate transformation to defeat the alien and scientist.
After the earth is saved they are finally at peace. Knowing that their deceased loved one would be happy with them. And throughout their adventure they learned to be more kind and openhearted towards others.