Dragon Ball vs Sonic

Connection:

Both are the grandest and most prized creations of mad scientists (Gero and Eggman respectively) hellbent on killing a main protagonist with golden super forms out of spite (Son Goku and Sonic the Hedgehog respectively). They were made as perfect lifeforms, with their sole purpose, their whole existence, being made to be better than others (Cell was made to be a perfect being above all others in every way and Metal was made to be a better version of Sonic in every way)

Because of their purpose, they'd grow a massive superiority complex based around them literally being made to be perfect (Cell grew a complex upon finally struggling against someone and realizing that he may not be the skit perfect being in the world, which directly goes against his philosophy of being perfect above the entire universe and Metal grew a complex based around him having to be a better version of Sonic, and that he was a failure as a thing in existence if he wasn't better than him in every way)

Both have been betrayed as arrogant, yet nigh-unstoppable killing machines who couldn't be matched. However, they eventually met their match by ironically the same person they were made to destroy. They would challenge their adversaries at their own game (combat and speed respectively)

Both get more powerful by advancing into higher forms by absorbing other inorganic things into their mass ( Cell gets stronger by absorbing other androids ((specifically #17 and #18) while Metal gets stronger by absorbing either data or metal objects) and also copying opponent's techniques).

Despite being made as the strongest of their class, they would eventually be outclassed by antagonists very similar to them who would dwarf them in power.

Both have a major contrast. Cell died the same perfection obsessed psychopath he always was. Still insisting on the incorrect assumption that he was the most perfect being in the universe. Metal, after getting defeated by Sonic so many times, came to a subtle understanding. Realizing that Sonic was the true Sonic, not him (this is further elevated by the IDW comics and the OVA)