Autistically forgot the picture, well fuck it. I'll put contribute to the thread instead.
My last point about Kaworu's arch came out a bit autistic, but, basically, if a being had the powers of the fruit of life and of mind (Adam and Lilith), it would become God-like. It would become "One", that is, lacking in nothing. Shinji was a Lilim and his existence was incompatible, by design, with the Angel's.
Much like how Adam's and Lilith's body merged to create super-rei -- a whole being --, Kaworu represented the possibility of Shinji filling the gap he sustains inside himself by acting like his father. Being Adam's soul, however, Kaworu had needs relating to that too: he too was not whole, and Shinji could not make him, either. Because he loved Shinji, he allowed him that one cruel choice. Also because Shinji could find someone else to give him dick, but Kaworu _kinda'_ had to destroy the world.
If anything Shinji's role is reactionary, not proactive. He didn't put a dog down, he was handed a gun by the Dog who knew he was in an early stage of rabbis and explicitly told _by the DOG_ what he should do. That's kind of how Shinji rolls, tho, no?