Sturzflug auf die Sünder

Because you consider only the characteristics of a double-faced card's front face while it's not on the battlefield, the types of its back face won't be counted for delirium.

If one of those creatures was enchanted, its Aura won't be put into a player's graveyard until after Descend upon the Sinful has finished resolving. If the controller of Descend upon the Sinful owned the Aura, it won't be in the graveyard in time to be counted for the delirium ability.

If you have three non-sorcery card types among cards in your graveyard at the time Descend upon the Sinful resolves, you won't get an Angel token. Descend upon the Sinful isn't put into your graveyard until after it's finished resolving.

In some rare cases, you can have a token or a copy of a spell in your graveyard at the moment that an object's delirium ability counts the card types among cards in your graveyard, before that token or copy ceases to exist. Because tokens and copies of spells are not cards, even if they are copies of cards, their types will never be counted.

The card types in Magic are artifact, battle, creature, enchantment, instant, kindred, land, planeswalker, and sorcery. Supertypes (such as legendary and basic) and subtypes (such as Human and Equipment) are not counted.

The number of card types matters, not the number of cards. For example, Wicker Witch (an artifact creature) along with Catalog (an instant) and Chaplain's Blessing (a sorcery) will enable delirium.