Of all of the series’ villains, J is the only one who actually won in the end.

No matter how you look at it, J entire goal throughout the series was to keep herself alive by any means necessary to the point she subverted all her redeeming qualities (including her friendship with Tessa) to do so, and eventually that’s exactly what she got in the end. Cyn has been defeated and her former teammates and Uzi are unlikely to go after her, which means she is now free and will likely retire from her villainy and start a new life since she no longer has any reason to keep killing. While she burned bridges with everyone she knows, she herself made clear that she fights only for herself and nobody else. All in all, of all the villains in the show, J is the only one who truly came out victorious, and not even in the way she expected.