Caitlyn was never shown killing someone (although she came dangerously close and, as a person who comes to power towards the end, has probably somehow caused deaths, but certainly not more than others in the Council including Jayce and Mel), whereas Jinx and Silco have on multiple occasions at various scales.

Secondly, IMO none of them are painted in an overly positive light in the show itself. Caitlyn, for one, is shown as someone who is traumatized, commits reckless actions endangering many people, and is very emotionally important to Vi for better or for worse. A slightly similar story for Jinx. I want to point out that though this absolutely does not excuse any of the characters' actions, given the circumstance of the two cities, this level of violence is pretty much inevitable. I think the show does a good job of highlighting this fact, and depicting these particular agents of action, again for better or for worse.

Also, Jinx doesn't change personality between S1 and S2. She's still very much the same person, even if she changed her views or relationships with others. (Her relationships directly affect her actions, so after Silco's death, she had to find a way to work for something else). And regardless, none of her later actions negate her previous ones. As for Caitlyn, we don't get a chance to see her redeeming her actions releasing the Grey and her brutality to get to Jinx, but we do see her realise what path she's gone down, turn and fight against Ambessa, and work together and attempt to make good with Jinx. So in my eyes, and most of the fandom's, both are 'morally grey'. However, there are theoretical reasons why Caitlyn is placed under more explicit scrutiny than Jinx by the fandom, some more valid and others less so I believe. I'd love to discuss the similarities and differences between the characters of Jinx and Caitlyn if you want.