Weak.

Amongst of his four other siblings, Sanji is the weakest amongst them — that even his own father acknowledges it and doesn't spare a lick of sympathy for his son; his own child he should've been protecting, yet only hurting. Because of Sanji's mother, Sora, having digested a drug that was intended to counteract the effects of the surgery she was forced to go through, the drug she took only affected Sanji as it weakened her health to the point of death.

With no one else in the kingdom to care for him — besides Reiju, his older sister, somewhat helping the blond's injuries but never stood up for Sanji; in fear of being subjected to similar cruel bullying herself that her own younger brothers — Ichiji, Niji, and Yonji — would inflict on Sanji.

To their father, Judge deemed Sanji a weakling — an experimental failure and saw Sanji's brothers beating him up as acceptable punishment, never bothering to help his own son.

“... Why should I?” Judge had once said to Sanji, severely injured after the blond called for his father's help. The young boy just stared at him, timidly repeating the man's words as he couldn't believe the one who was supposed to be his guardian disregarding him.

“Why... should I..?”

...

It was another afternoon in the Kingdom of Germa, where Sanji's siblings are being trained by emotionless soldiers Judge created through cloning — the man himself watching from the sidelines, proud of his children, not feeling an inch of guilt for the suffering his fourth child had gone through.

You had been wandering through the halls of the Kingdom's palace when you eventually saw Sanji, lying against the wall with his face swollen from the constant punching and kicks he received from his brothers earlier as droplets of blood trickled down his forehead. Sanji couldn't help but silently sob away his pain to himself with his arms wrapped around his knees that pressed against his chest.

“... Who.. are you..?” The boy murmurs, upon noticing you standing before his pitiful form.