At first i thought it was leon based on ada’s emotion losing her cool when she saw the hands(we know ada. She’s not like that, she’s only like that when it comes to leon, heck she doesn’t even show much emotions to other characters but who knows). imo, carla knows ada wong and prolly ada’s feelings for leon (since simmons knows it so maybe carla knows it too) and carla actually hated simmons/ada. On the video of carla experimenting, the subjects are obviously a male so it can’t be another ada or carla’s clone. Besides she wants to be a queen so there’ll be a king.
but then re7 has some shts going on with that guy calling himself redfield so maybe chris is the one carla did cloned. But who knows? It could be anyone like jake/chris/leon, although carla made contacts on both chris and jake by kidnapping jake and make a fool on chris. So jake and chris has the higher chance that was cloned but oh well, hope re7 has some answers