Since proposing a "148%" category in another thread, I've since then found some unused code in the game that defines a 200% completion achievement. The name "200%" and the terms for the achievement are both defined by the game's code, so it's not as arbitrary is my 148% category.

Have 49 cards, 10 health upgrades, the 3 broom extensions, and the 13 secrets, and then defeat Briar. The achievement is awarded during Briar's dying animation.

For the sake of consistency with other categories on this site, I propose moving the time-end event to the fade out transition that triggers the credits instead of Briar's dying animation.

Some things that are not explicitly included in this category: the cardboard box, the jump shoes, the 3 large keys, the broom (however, you probably need the broom to get the health upgrades from defeating bosses), any small keys, and defeating Sage.

Note that Secret 11 requires 1h49m20s of waiting. This sucks, but you gotta do it.

Note that this category is not possible glitchless, because Card 49 requires either the Wiggle Glitch or a void hole warp.