The Binding of Isaac: Rebirth

Secret Achievement - Kill Isaac with Eve
Eve is unlocked by not picking up hearts for 2 levels, this just means, do NOT pick up hearts for 2 floors. Picking up items that give you extra health or soul hearts is fine! just make sure that they weren't picked up hearts!
To unlock the floor to actually battle Isaac is unlocked by defeating mom's heart 11 times.
After you meet these criteria you will be ready to get this achievement! First you will enter the first floor, i recommend getting items that increase your soul hearts and black hearts, but reduce your red hearts. Typically you only want 1 (or less) red hearts, as it activates Eve's ability "The Whore Of Babylon" which increases damage. A way to reduce your hearts to one upon entering a room but also keep your heart on the side is, if you have another controller, press on it and enter the room the press it again, giving you the ability, but allowing you to keep the hearts! This is especially useful on the first floors to speed them up and make them easier.
Its a fairly easy achievement, just requires some practice with her. Some really good items and abilities for her are most items that increase damage and give soul hearts, which you will find in devil rooms a lot. So bomb shopkeepers if you can and that will help cause Devil rooms to spawn. In the early floors (the first two) if you don't get items that you like, like soy milk, or a boss you just hate, and you know will take a lot of your hearts, its recommended to just quit and restart the run, as the first floors are really the cement that holds your final battles and help you progress without much interference.
As you approach the final battle with isaac, you will enter the cathedral, this is a single floor level. Meaning you won't have to progress through multiple floors just to get to the boss.
When you arrive at the boss room you will see Isaac laying on the floor crying, this is stage one of his fight, and he has 4 attacks during this first stage, which are:
-He fires multiple shots in the player's direction.
-He shoots 12 lines of tears in every direction.
-He shoots 8 groups of tears in a spinning pattern.
-He shoots 8 groups of spinning tears together with 8 lines of tears in every direction.
This stage is fairly simple, just stay back and fire at him avoiding his slow moving shots, i usually cling to the wall on the right and just move up and down as he fires at me.
When you take him down enough, you will notice he gets up, this is stage 2, but now he gains 3 more attacks:
-He shoots 4 tears in the cardinal or diagonal directions, which will split into four short-ranged tears after a short time.
-He spawns 2 Angel babies that fire at you and teleport away from battle after short time.
-He drops two beams of light from the sky in random locations.
This stage you will have to move a little more, avoiding his shots and shooting yours back at him, as well as constantly taking out the angel babies he spawns. After you take him down enough, he will sprout wings and start flying around, this is stage 3, and with a new stage, more attacks. He will now have the ability to teleport, like the angel babies also firing 11 faster moving tears at you, but he no longer spawns the angel babies!
-He fires multiple shots at you
-He will spawn a bunch of beams of light, like in stage two, but now in a pattern, moving from a top corner, travelling to the opposite bottom corner
He will also move in at you as you try to get behind him, attempting to block you from getting there. This stage is fairly simple as well, but be careful for the beams of light, as you see him teleport and spawn the beams of light, quickly head to the top left, or top right corner, wherever the beams aren't, they will usually miss you. Just keep laying into him, avoiding his attacks and you should whittle him down until he falls and flies away and a chest will spawn in. And congratulations! You have completed the boss and the achievement is yours! Just hop in the chest and the item and the achievement are yours!