Best rivalries of the 90’s - Sonic and Knuckles

Best rivalries of the 90’s - Sonic and Knuckles from Sonic the Hedgehog 3 (1994)
In the third Sonic game the blue hedgehog faced the island’s guardian, Knuckles the Echidna. After Eggman's trickery Knuckles became a good friend and rival of Sonic.
If you grew up in the 90s you know that in many cartoons, comics and videogames there was an intense rivalry between two main characters. Every kid had his own favorite character back then, so which one was yours?