Cult of the Lamb

Easy solution. Playing on easy I used the fleece of the glass cannon to double curse damage and waited for a run where I got hands of the fate (the one that shoots a bunch of projectiles) and just spammed it. Died in seconds, didn’t even get a single wave of enemies out

I'm going to post a few quick tips for beating all of the bosses without taking damage.

First, which is something that I didn't realize you could do until after I had already got all of these achievements, turn down the difficulty to easy. I'm regretting not knowing this one, as I did all these achievements on extra hard and for your sanity don't do this.

Second, since you're going to do a flawless run of the boss, use the golden Fleece , as their is really no downside to using it since you won't be taking damage.

Third, I would recommend doing these achievements after beating the game and getting all of the tarot cards. The tarot cards that I went for are ones that would increase my damage on my weapons or curses. Specifically, I went for ones that made it cost less energy to cast and if you can get them the one where curse energy is refiled on entering a new room or the one where it slowly recharges.

In terms of weapons I used:
I like going for the axes they deal enough damage to kill enemies quickly but aren't as slow as the hammer making you entirely susceptible to damage. This is entirely up to preference though. Although the faster you can get though the fights, the less chances you have of getting hit. I like trying to find godly weapons for this reason.
As for curses:
I used curses that swiped and knocked back enemies as well as projectile attacks. I mainly saved my energy in case of emergency to knockback incoming attacks. Some people might want to play the range game and that's fine as well.

IMPORTANT
This achievement can be made trivial if you can get lucky enough. While looking for which path to take, look for a modifier that looks like a sword between two hearts. This will make all enemies health is halved but you also receive double damage. This includes the boss you are trying to do without taking damage. I would go through the floor try to rack up as much damage bonus from the golden fleece and then go to the statue and kill the boss really before they have a chance to think about the sins they've committed.

Also as a quick tip, if you can do the brainwashing ritual before you leave, if you care about your followers. You may be gone for a while.