Hiruzen was possibly the worst hokage in Konoha history. He ended 3SWW by just giving up while Konoha was winning, he enabled Danzo (and his old team mates) to commit a genocide, he let Orochimaru go initially, and he failed to keep his promise to Minato and Kushina to take care of Naruto.

Sure, Tobirama is also to blame for the fate of the Uchiha, but that's pretty much his only major failure (apart from naming Hiruzen his successor I guess).

@McGallant He gave up during the war? Could you clarify that statement; I don't recall.

Hiruzen is arguably the worst Hokage.