The Hundred Days Offensive Jul–Nov 1918 was the costliest
The Ludendorff offensive other wise known as the spring offensive was a German offensive on the Western Front intended to win the war before the American troops that had begun arriving in France could fully deploy.
I'm unsure of how far they advanced
Kaiserschlacht was the last German offensive and was a series of German attacks along the Western Front.
Indulgences
Hus opposed the sale of indulgences. Indulgences were documents of personal
forgiveness from the Pope which were sold for sometimes exorbitant prices
to raise funds for Crusades. he also called for preaching of the bible in all languages and also the giving of full communion to church members. In addition, he also called for higher morality among priests.
I believe that the cash crops and the need for those cause a lot of slave trading. Americans used a lot of slaves to help build up cash quickly.