I couldn't see the answer to this question but I know you have to beat certain bosses several times, and I know the fight between Mom's heart is replaced, but how many times do you need to beat the game before you 100% it?
Okay because for 100% the answer would be infinite due to the 100% requirements require you to pick up every single item in the game Here are the bare minimum requirements to get every non-RNG boss related task done.
First I am making some assumptions here.
- First you are playing as one character the entire time until the last step.
- You are not picking up any items that transform you into another character Ankh or Judas' Shadow for example.
- You never die and have to start over again.
- You are playing on Hard mode to start with.
- This list assumes you are unlocking all the characters during these runs and not requiring extra runs to unlock them.
- We manage to get Boss Rush at during one of the runs on each character
- We manage to get the Key from to unlock the Mega Satan room on one run per character after killing either Lamb or ???.
- We manage to kill hush once for each character.
- You manage to unlock The Lost before fighting Mom in a run.
Okay so here we go.
One kill unlocks Mom's Heart.
Killing Mom's Heart 11 times unlocks Sheol and Cathedral (requires 11 Mom kills as well)
Killing Isaac and Satan 6 times each unlock the negative and Polaroid respectively. (Plus 12 to Mom and Mom's Heart kills)
Killing The Lamb and ??? unlocks an item (Plus 2 to Mom and Mom's Heart. Plus 1 for Isaac and Satan.)
Each character after this adds 2 Mom kills, 2 Mom's Heart kills, 1 Satan kill, 1 Isaac kill, 1 Lamb kill, and one ??? kill. Multiply the number of kills listed by 12 and add them to the lists (since we already beat the Lamb and ??? completely with one character.
50 Mom kills
49 Mom's Heart kills
19 Satan and Isaac Kills
13 Lamb and ??? kills
13 Boss Rushes
13 Hush Kills
13 Mega Satan Kills
BUT WAIT THERE IS MORE!
Who could forget about the challenges!
Add 30 Mom kills since every challenge at least requires Mom.
Add 17 Mom's Heart kills taking out challenges for Mom only.
Add 3 Satan kills for challenges ending in Satan (No challenge ends in the Lamb)
Add 5 for Isaac for challenges ending in ??? or Isaac.
Add 1 for ??? for the one challenge ending in ???
Add 1 for Mega Satan due to the challenge ending in a Mega Satan kill.
But what about greed mode?
Well with greed mode we need it to unlock one of our special characters for our completion. Some more assumptions with greed mode.
You are donating 50 coins a run to the greed machine.
You are switching characters regularly to get all the items from greed mode unlocked.
You are playing on Hard.
Okay so now that assumptions of greed mode are done we can do an easy calculation by dividing 1000 coins required for the character by 50 which we are donating every run giving us.
- 20 Ultra Greed kills
Which will max out our greed machine allowing us to complete the game with all characters.
Which brings us to the moment of truth
To beat all the non-rng content including the main game and challenges you need to kill.
66 Mom's Hearts
20 Ultra Greeds
14 Mega Satan
13 Boss Rushes
So it would take between 101 to ∞ runs to unlock beat all of the boss related content 80 runs for Mom and the main game. 20 runs for Greed mode, and one extra run for the Lost.
Technically you could 100% the game in 101 runs if you managed to get absurdly lucky with RNG and manage to pick up every possible item in the game during your time playing but this is nearly impossible to happen.
Good luck trying to get only 101 runs to unlock all the content!
You cannot get 100% completion simply by beating the game a bunch of times. There are several things you have to do to 100% the game:
Beat all challenge runs (High Brow, Waka Waka, etc.)
Unlock all items by finding/completing all secrets
Collect each item at least once (must be done in a non-seeded, non-challenge run) (can be done over the course of multiple runs)
Complete each character's "post-it note" by completing runs in hard mode. This must be done for each character, including the secret character(s).