Although I generally prefer working in mid-sized startups over large corporations, there are a few important lessons that I picked up and will be thankful for from my time working in a bank:
1) Processes - When a business is growing and picking up speed, processes allow for more streamlined operations, clearer communication and more efficient output
2) Being concise - When you're speaking to your bosses who have had 30 years of experience in the corporate world, you have minutes to deliver your point across. I used to get cut off by my ex-boss for not answering his questions within the first sentence. It's a skill that I found really helped me keep future conversations with others short and snappy, without sacrificing value.
3) Resilience - Some of the toughest people that you will meet are in corporates. It may suck at the time to have to answer to or deal with them. They will critique your work, attitude and performance with little to zero filter. But it's these people who will help you build up the thick skin that can and will take you places as your career progresses.