Who Was More At Fault?

[Yoshi]

When it came to Cell becoming Perfect?

 

[Giga Hertz]

Krillin genuinely felt like he was murdering someone who hadn't necessarily done anything overtly wrong.

Vegeta wilfully did everything in his power to ensure Cell's perfection. While Krillin had the opportunity, he was also trying to prevent it through other means.

 

[Yoshi]

Yeah, and in the context of the actual story, Piccolo even mentions to Bulma that Krillin broke the remote and after saying that he also said that Vegeta ruined everything.