World War II - axis powers

Reich: Convinced the most powerful players in the sector to essentially hand over most of their earlier conquests, pioneered the art of mobile warfare and used it to take over the most powerful country in the region, advanced the art of rocketry and jet engine technology and helped to perfect a class of infantry weapon that became the mainstay of armies to this day.

Japan: Perfected the art of inter-war carrier combat, was the earliest country to discover and use tanks with infantry support, was the only axis power to be successful in amphibious warfare.

Hungary: Was the only "minor" axis power to achieve indigenous tank production, successfully copied the Panther into a better tank, had success in the east and got invested in by the Germans to the point where they acquired Panther and Tiger tanks.

Bulgaria: Was the most successful of the minor axis during the early stages of Barbarossa and acquired modern equipment from the Germans. They did, however, switch sides soon afterwards.

Italy: Went into the war with a shockingly appalling industrial base, couldn't equip their army even with the German's help. Failed to invade Greece, twice, opened up a second front in Africa and permanently crippled the Germans logistical capability and eventually became the first front on the European Continent that the Allies broke into.

You can argue the size of the role each faction played, but the Italians almost worked in detriment to their cause rather than for it.

Those who lost a war typically would prefer if you forgot their involvement.