Kowalski analysis:
Filter 1: Punched by Luffy intentionally
- Zoro
- Usopp
- Sanji
- Vivi
- Franky
- Yamato
Filter 2: Intentionally hurts Luffy and Luffy's teammate(s)
- Sanji : WCI
- Vivi : Mrs Wednesday shenanigans
- Franky : KO Usopp
Filter 3: Have opposing ideology
- Sanji shares food (entire story), Luffy doesn't
- Vivi is being naive/saving everyone is possible (Alabasta), Luffy knows victims will appear
Filter 4: Have opposing method to reach their dreams
- Sanji's dream must not follow known islands & go to unknown areas, Luffy's dream must follow each island in Log Poses.
Additional proof:
- Zoro : Luffy hugs Zoro when they reunite, Luffy fights Sanji when they reunite. Luffy is born blessed like Zoro, Sanji is a mediocrity
- Nami : Luffy always follow Nami's order, but he always ignore/disobey Sanji's (mainly food & plans)
- Usopp : Luffy doesn't mind bazillion Usopp's lies, Sanji lies once and Luffy confronts him
- Chopper : Luffy keeps trying to make Chopper joins repeatedly, he stopped inviting Sanji when he doesn't want to go
- Robin : Luffy fights the entire World Government for her, Luffy only oppose 1 Emperor for Sanji
- Franky : Franky's pervertedness doesn't cost SH anything, Sanji's pervertedness cost SH a lot
- Brook : Got invited by Luffy at the first sight, Sanji got invited after he shows value
- Jinbe : He is there when Luffy lose Ace, Sanji didn't
- Yamato : Yamato risked her life getting killed for Luffy, Sanji is the only SH to almost kill Luffy
Conclusion, Sanji is the answer.