Some of them have more than one important contribution, but I only listed the one I consider the most important of them.
Kin'emon:
He met the strawhats and somehow got them and the Heart Pirates to fight alongside the Kozuki Clan.
Kanjuro (to the enemy team):
He rendered both Ashura and Kiku out of commision during the raid.
Inuarashi:
He defeated Jack.
Nekomamushi:
He did crucial damage to Jack.
Raizo:
With the help of Jinbe, he stopped the fire at Onigashima, saving many members of the alliance.
Kiku:
none
Ashura:
He got the blueprints from Kaido's castle, allowing Law to elaborate a better plan for the raid.
Denjiro:
He saved many of the raid's allies from Orochi (including Hiyori and the samurais who were imprisoned in the Flower Capital).
Kawamatsu:
Without him, Onimaru wouldn't have gathered the swords for the allied samurais to use.
Kin'emon:
He met the strawhats and somehow got them and the Heart Pirates to fight alongside the Kozuki Clan.
Kanjuro (to the enemy team):
He rendered both Ashura and Kiku out of commision during the raid.
Inuarashi:
He defeated Jack.
Nekomamushi:
He did crucial damage to Jack.
Raizo:
With the help of Jinbe, he stopped the fire at Onigashima, saving many members of the alliance.
Kiku:
none
Ashura:
He got the blueprints from Kaido's castle, allowing Law to elaborate a better plan for the raid.
Denjiro:
He saved many of the raid's allies from Orochi (including Hiyori and the samurais who were imprisoned in the Flower Capital).
Kawamatsu:
Without him, Onimaru wouldn't have gathered the swords for the allied samurais to use.