What was the most significant career moment for Chandler on Friends?

Chandler Bing's career on Friends was a significant storyline throughout the show's 10-season run, with the character experiencing numerous ups and downs in his professional life.

However, one of the most significant career moments for Chandler came in Season 9, Episode 9, titled "The One with Rachel's Phone Number." In the episode, Chandler quits his high-paying job in advertising to pursue a career in data processing, something he is genuinely interested in, even though it pays less. This decision is in response to the wake-up call he receives after taking a quiz to determine his dream job, which reveals that he has always wanted to work in data processing.

This episode represents a pivotal moment for Chandler's character as it showcases his development and growth as a person. It also emphasizes the importance of following your passions instead of just chasing money, something that Chandler struggled with throughout the series.