Chuck believing in Blair. 4x13 and 6x03.
She’s a force to be reckoned with and Chuck always knew it. He always believe in her even when she didn’t believe in herself.
The many times she doubted herself he never stopped showing her she WAS powerful.
The thing is Blair only EVER insisted on making something of herself when she was planning her future with Chuck.
With Louis she settled for the throne and the title, setting aside any desire to be powerful in her own right, disregarding her independent nature.
With Nate she was the perfect society prince on the arm of the Golden Boy and with Dan she was Claire. A mere shell of herself.
But she only ever wanted to be EQUALS with Chuck.
First it was because she didn’t think he was worthy of her (when he broke her) and then because she wasn’t of him, she couldn’t let him pay her dowry because then she wasn’t Chuck’s Blair and she just wouldn’t have that.