sanji dead ass always want to die bruh, i'm guessing that is his weakness ?
It's a matter of balance.
He puts others' way too much ahead of his own life.
His motivation for self sacrifice is tainted with a self deprecation of his own value. Something that comes since his intro in Baratie.
He thinks "dying" is the way to repay other people's kindness towards him, probably tied to his childhood with Germa.
What he needs to do is start accepting that his own life is worth it, and "dying" for others is not as noble as he thinks. If you die, you can't protect anyone anymore. you can't repay anyone anymore.
His mother didnt sacrifice herself so Sanji can go die.
Same as Zeff.
That's the main thing he must overcome. Once he does that, he can become the "unbreakable shield" that he is meant to be.
A full cycle.