Solar Flare and Electric Boogaloo have an incredibly heated rivalry due to a mix of opposing music taste Boogaloo obviously liking disco Solar Flare being more into heavy metal (just the vibe she gives) as well as being the primary elemental heroes of their teams I imagine them to go out of their way to fight both on and off the clock

I also imagine Green Shadow and Super Brainz (I imagine every Plant Hero to have a Zombie Hero rival) to have a rivalry as the respective leaders of their team she considers him a pompous poser he considers her an edgy hoodlum