Tezuka Osamu no Buddha: Akai Sabaku yo! Utsukushiku

An endless war between two nations, and a rivalry between two great men; one of them is ambitious, the other one is a peace seeker. 

At the ancient times, these two anime depicts the cruelty of the era of wars and revolutions, with themes such as class society, slavery, injustice, and ambitions. 

These anime are based on two famous Osamu Tezuka's manga, featuring plenty of characters and large-scale historical plots revolving around a legendary spiritual entity (Phoenix and Buddha respectively). Besides, both are dramas with quite a lot of deaths. 

Both are films depicting the file of the Buddha While El Cantare is a narrative on how Happy science accounts for the creation and history of the world - with the Buddha's life being a climactic part of the story, Akai Sabaku is specifically about the Buddha's life and works.