The Reddit AMA took place in April 2015, shortly after the first season of Breaking Bad spin-off Better Call Saul wrapped. When asked which Breaking Bad character struck him the most, Gilligan replied:
“I have to say, the death of Walter White hit me the hardest because it represented the end of the story and the conclusion of this seven year journey that we – the cast, crew, writers and directors of ‘Breaking’ – have taken together ‘ Bad.’ That was the most moving death I could write. I actually got tears in my eyes while writing it.
It’s clear from Gilligan’s response that the tears weren’t so much about Walt’s tragedy as it was about what it meant to him to end the series. Making ‘Breaking Bad’ was a long road – Gilligan has previously spoken about how several networks turned down the series before it found a home at AMC. Along the way, he forged creative partnerships and secured his legacy as one of television’s great writing talents. Creating and making something happen is a profound experience, worthy of tears.
Gilligan added to his response, “I think a close second [in terms of most affecting] was the death of Mike Ehrmantraut.” Gilligan didn’t elaborate Why He feels that way, but it probably has more to do with the context of the scene itself.
https://www.slashfilm.com/1232743/the-breaking-bad-scene-that-brought-showrunner-vince-gilligan-to-tears/ Walt’s death brought Vince Gilligan to tears