Someone that could be manipulated into believing it was the right thing to do, or someone that could be persuaded into it with rewards. Unfortunately, that describes the vast majority of humanity. They're fickle creatures.

[ it sounds like he's about to throw barnham under the bus again, but, miraculously, he resists the temptation. ]

It isn't me. I can reasonably assume that it's not you or Noctis, either, nor Shinnosuke or Damian, and it's very unlikely to be Percy, considering his... reaction. That leaves Barnham, Jason, Rin, Papika, Lecter, Will, Xion, Natalie, and Okabe as our suspects.