Just Strawhats?
Shell Town: Zoro, only option
Orange Town: Zoro, rescued Luffy and Nami from Buggy
Syrup Village: Zoro, beat the brothers, carried Usopp to Jango, cut down a branch that let Usopp snipe him
Baratie: Sanji, only real option since Zoro vs Mihawk had nothing to do with Krieg
Arlong Park: Zoro, beat Hachi and most of Arlong‘s crew, held off Arlong while Sanji went to rescue Luffy
Loguetown: Well, Zoro beat Tashigi, so I suppose that’s something? Nobody did much.
Reverse Mountain: … I can’t remember anyone doing anything standout. Nami gets a log pose, so she kind of wins by default, but really it was Crocus.
Whiskey Peak: Zoro, fought off the bounty hunters
Little Garden: Usopp, helped fight with Luffy while Zoro, Nami and Vivi were captured and Sanji was wandering
Drum: Chopper, saved Luffy, Nami and Sanji, beat Chessmarimo
Alabasta: arguably Robin, since she saved Luffy and didn’t tell Crocodile about Mr Prince. If not Robin then Sanji, for Mr Prince and beating Mr 2
Jaya: Robin, I think? She found out the info about Cricket and caught the South Bird.
Skypiea: Nami, without her Waver skills Luffy couldn’t have beaten Enel
Long Ring Island: Zoro, gave Chopper a man-up speech, him and Sanji won him back, then took charge when Luffy started fighting Kuzan. Chopper did well to help the recovery from Aokiji’s freezing as well
Water 7: Sanji for going on the Sea Train after Robin
EL: I’ll give it to Franky, him and Usopp helped snap Robin out of her darkness funk, he destroyed the Pluton blueprints, beat his guy first, saved and protected Robin, the Sunny. This is the arc all the Strawhats stepped up in their own way to save Robin though.
Thriller Bark: Zoro, beat Ryuma to get Brook’s shadow back, led the line against Oars in Luffy’s absence, took on Kuma, took on Luffy’s pain
Saobody: Sanji, got Duval on-board which allowed the crew to gather at the auction house
Amazon Lily: N/A
Impel Down: Jinbei, only option, but also was vital in escaping ID
Marineford: again, only option, again, was really important throughout, protecting Luffy from Sakazuki, snapping him out his misery
Fishman Island: Jinbei, without his blood Luffy dies
Punk Hazard: (Law) but since I can’t count him… Sanji? Saved Kine’mon, delayed Vergo, got G5 to subdue the kids
Dressrosa: Usopp, gets the Grand Fleet onside, took out Sugar twice (and the second time was cool enougn to make up for the first.
Zou: Chopper, probably? Saves the Minks from Caeser’s gas, helped Zunisha recover after Jack’s second attack
WCI: very difficult, but Brook just edges out Jinbei for being a boss the entire arc, getting a Road Poneglyph, smashing the Carmel photo, ripping the piss out of Big Mom
Wano: Zoro, helps save Bakura Town, saves the arc princess, discovers weapons for the raid, gets the anti-bodies for Chopper, fights Kaido with Luffy.
Final scores
Zoro: 9
Nami: 2
Usopp: 2
Sanji: 4
Chopper: 2
Robin: 2
Franky: 1
Brook: 1
Jinbei: 3