Garnet

Garnet always reminded me of the pre-flanderization Knuckles. Seriously, they're both reddish, socially stoic fist-fighters with barely used electrokinetic abilities who can hang onto walls with their fists and they both have a hair style associated with black people. Come to think of it, there are more parallels like that: Peridot is similar to Tails as they are both smart mechanics who at some point built mechas to run around in, Peridot had helicopter fingers while Tails has helicopter tails and they're both really small. Jasper is similar to Shadow, they are both called the "ultimate one" of their kind, have stripe pattern on their bodies, have extraordinary fighting skills including a spin dash attack and hated the Earth because they blamed it for the death of someone they cared about. And I guess you could make a parallel between Lapis and Blaze as well, they have strong elementary powers and were asocial due to bad experiences, but the main character helped them out and Lapis was possibly a very important Gem before the war while Blaze is a princess. But that one's a little vague because we don't know much about either Blaze or Lapis.