JoJo's Bizarre Adventure - Jotaro died for nothing.

Joseph was right all along.

He told Jotaro not to lose his cool when he was fighting DIO.

Jotaro lost his cool and killed DIO with the power of his rage.

The second and last time Jotaro lost his cool was when Pucci threw knives at Jolyne and triggered Jotaro's PTSD and fear for his daughter.

Even Pucci admitted that Jotaro was only one step too late. Jotaro chose to save Jolyne instead of logically killing Pucci first and possibly saving everyone.

Jotaro got himself and most of Part 6's cast killed because he lost his cool.