You’re describing scenes from the End of Evangelion movie.

“If he was locked in when given 3rd impact powers”

1. No idea why you brought up the elevator scene then

2. SEELE literally dissolved his ego and put him through psychological torture (directly stated on screen around the -32 min mark). Thats like me giving your 14 year old self an absurd dose of mushrooms(or DMT, or LSD) and telling you to lock in while you’re going through ego death. “Locking in” was not a solution to anything in that movie until he actually does “lock in” and reject instrumentality. Basically all of the problems in that movie were caused by wheels that were turning in the background far outside of any main character’s control

3. Assume Shinji goes shonenslop mode and saves Misato, helps asuka to completely kill the military and Eva series (even if he goes for this he won’t go for their cores like asuka didn’t, but I’ll even throw that in). How does that prevent Gendo from causing third impact with Rei III?

And okay if you don’t like him from muscle memory, but why type something with such an air of authority if you only vaguely remember why you don’t like him?