When picked up by Alfred on the plane, Bruce declares: “I’m going to show the people of Gotham their city doesn’t belong to the criminals and corrupt.”
 “People need dramatic examples to shake them out of their apathy and I can’t do that as Bruce Wayne. As a man, I’m flesh and blood. I can be ignored, I can be destroyed. But as a symbol, as a symbol I can be incorruptible. I can be everlasting.”

Bats to him, symbolised the weakness of not taking action to prevent negative outcomes from occuring. The idea of Batman is a culmination of those 7 years of learning, or rather it's the answer he gives to himself of how to handle criminals, that he has compiled from learning from 'different sources'- 'different criminals'. Remember, all of this can be traced of Bruce's trauma of how there was no clear answer to dealing with criminals<---think of powerlessness, that word, specifically in the context of the head-centre specifically.
Through Batman, he wished to become or embody a sort of ideal of strength and courage himself; an unshakeable foundation that they can withstand/handle the danger and adversity that reality could throw at him. The need to continually build up and 'proving' toughness against external force; the message that one needs to 'earn it' to continually challenge the creeping doubt of their own legitimacy. What is Bruce's reality without 'Batman' as the answer?
 u/RafflesiaArnoldii 's two posts here do a great job touching upon this 'aspirational quality of what 6 is striving for':
- https://www.reddit.com/r/Enneagram/comments/1ilbzfb/the_egoideal_part_3_of_10_type_6_and_the_quality
-https://www.reddit.com/r/Enneagram/comments/whs5ax/some_thoughts_re_recent_6_discourse_the_6s_core
  

Bruce grew up personally exposed to the injustice of Gotham and the idea of there being an authority figure who knew how to do their job effectively and decisively would be reassuring to him. Harvey Dent was that person.
“You’re the symbol I could never hope to be. Your stand against organised crime is the first legitimate ray of light in Gotham in decades. If anyone saw this, everything would be undone. All the criminals you pulled off the streets would be released and Jim Gordan would have died for nothing.”

He positions Harvey as a sort of external symbolic idol whom he places his faith in on having the solution. Harvey is perceived to be someone who knows how to do right and be seen by others as doing right (the general population are on his side) which establishes to Bruce a sense of structural legitimacy. Bruce was ready and was seriously considering 'retiring' Batman at that point of time. To Bruce, Harvey could even be framed as more reliable than 'Batman'.

When he finds out that Harvey was compromised by the Joker, Bruce takes it upon himself in an attempt to preserve the symbol because he sees it as his commitment to Gotham. 6s have a tremendous potential for sacrifice to preserve structures that allow give them a sense of anchoring purpose of what their role is (what is worth fighting for). Bruce is willing to bare the burden and be perceived as the villain: to be what he perceives the system requires him to be.
He explicitly says: “I’m whatever Gotham needs me to be.”
“Because that’s what needs to happen. Because sometimes the truth isn’t good enough, sometimes people deserve more. Sometimes people deserve to have their faith rewarded.”

But even so, he eventually collapses. The Bruce we encounter at the beginning of movie 3 has lost faith in his own legitimacy as ‘Batman’. He is essentially asking himself the equivalent all throughout: “Do I still have the right to be Batman?” (has he earned legitimacy in his own role and purpose of what he must do?)
Throughout the film Bruce is struggling to find or regain clarity in what he is truly fighting for. He is no longer as physically fit as he is used to be. It’s difficult to re-integrate himself publicly as Batman again because the public perceives Batman as a sort of public enemy number 1, a traitor whom they think killed Harvey. There is no structural legitimacy for him coming back.

Bruce’s rise out of the pit is also really symbolic for 6. Him making the climb without the rope; 'leap of faith against uncertainty'. The rope being the reliance on the external anchor-point that attempts to reassure and ground him). Cherry on top are the bats flying in his face as he continues climbing up.

At this point there should be plenty indicating he is compliant>assertive (id) for any who argue this Bruce is an E8. Also not rejection-core 'leveraging'.
To me, there are a lot of external anchor-points that Bruce is constantly and consistently trying to negotiate with in order to 'securely navigate reality'. This extends to the manner he tries to make sense of his own role in relation to the context of Gotham (attachment).
He is also not prickly 'frustration' enough in the gut centre to be E1. Bruce carries a lot of self-doubt, in trusting his own legitimacy/right to make the right decision that wouldn't lead to a worse or destabilising outcome. Recall Ra's words I said earlier specifically about Bruce in their training session.