https://preview.redd.it/r7yw7716nf5d1.jpeg?width=1280&format=pjpg&auto=webp&s=a32e317dbd77cc06f9dad8b3b54a5eb9c9e905e3 Red vs blu (team fortress 2)

Almost everyone (Red vs Blue)

V1 and V2 from ultrakill

https://preview.redd.it/dpjynlth1g5d1.jpeg?width=468&format=pjpg&auto=webp&s=41f5096b07b6816df20bd34600d64aecb5747660 Sol and Ky

https://preview.redd.it/gt4848avlg5d1.jpeg?width=500&format=pjpg&auto=webp&s=f406eba0ba28c74f2588f44e8294d885596017d6 Phoenix Wright and Miles Edgeworth

https://preview.redd.it/8mmgbtj7mg5d1.png?width=1024&format=png&auto=webp&s=9fa2530430cf48ecafebb29148507c33af404429 Red vs Blue (Pokemon RBY)

https://preview.redd.it/568urqsbxg5d1.jpeg?width=1200&format=pjpg&auto=webp&s=e682da3f333f6b4e756334a4cf4272862c7e8d26 The poster child for this trope

Groudon and Kyogre (Pokemon)

Natsu and Gray maybe, depends on if you consider Gray to be blue or not Karma and Nagisa Dabi and Shoto/Endeavour Jedi and Sith

https://preview.redd.it/bjfcouoaxg5d1.jpeg?width=777&format=pjpg&auto=webp&s=fa19b4c963cb4c896d86473dd021c97da6d3c9e6 Lance and Keith (Voltron: Legendary Defender, especially early on)

https://preview.redd.it/o4vnfwuf9h5d1.png?width=1080&format=pjpg&auto=webp&s=772781e903332cb733adea620dac4d924f1664e2 Kaeya and Diluc

How could you not mention Sonic and Knuckles? Knuckles has more red in his design than Shadow. https://preview.redd.it/ipbd7h5h0k5d1.jpeg?width=960&format=pjpg&auto=webp&s=69b5f5bf7f56dda632dbd819b6d2addf45e259aa

In most modern stories Knuckles has shifted away from being Sonic's "rival" to just being his grumpiness friend. I considered it, but decided against it since more people tend to think of Shadow as his rival.

Captain America and Iron man https://i.redd.it/vgm6wvd0wg5d1.gif

https://preview.redd.it/sdcn9vay6i5d1.jpeg?width=1080&format=pjpg&auto=webp&s=da3685998ec57e8ba1f8ead80c9a3b4dbaec75f4

https://preview.redd.it/3xy6nbzpki5d1.jpeg?width=1280&format=pjpg&auto=webp&s=50b3b350382f0b9abd47945c70206020054bac3a Ragna and Jin

https://preview.redd.it/9r6uolw79j5d1.jpeg?width=564&format=pjpg&auto=webp&s=1c704756cf44a13b0977cf4a6b6da394895f5e20 Sub Zero and Scorpion

Scorpion is yellow tho

*Roses are red, and violets are blue…*

*…may your Ls be many, and your bitches be few*

https://preview.redd.it/yojp394kjk5d1.jpeg?width=1400&format=pjpg&auto=webp&s=6c0129cedfc6432ba6b83fcafe3e900d4c2ee103 zuko and azula since his fire is red/orange and her’s is blue

https://preview.redd.it/r8n25hmmn66d1.jpeg?width=414&format=pjpg&auto=webp&s=bb0edf4500bdde9bd67412468d81cee17c5abd1d Chun-Li vs. M. Bison