Ring of Pain

The hardest part of this Achievement for me was reaching 5 Hp, not surviving.

If you have no idea how the game works and can't complete a run smoothly, wait until you have enough experience

Overall you have to build a solid build but at the same time lower the Hp (unless you are lucky enough to find the room that reduces the Hp, it depends too much on luck so I will not take it into consideration)

Useful items:

Camouflage: Cancels ranged attacks, that would be lethal given the HP
Plague: +3 Poison to target then double the poison; this destroys any enemy including bosses
Stone caller: Inflict 2 petrify to all enemy when take damage, this can kill the whole room if you have a high defense

If you have completed a Run without discarding items, you can use the Backpack. The Backpack allows you to use the Frozen Tiara with a full build, this means killing anything as long as the speed is over 21.

In short, it is not that difficult if you are familiar with the game, it is just a matter of patience and attempts

I don't think one of the endings is better than the other, it all depends on what items you have

With the Multiclass update, there's now a way easier method of getting this achievement, thanks to a new item.
With the item Soul Stitch, if you die, you ressurect with 5 * the number of Soul Kin items equipped, so if you die with only one Soul Kin item, you ressurect with 5 max health.
All you'd need to do is get Soul Stitch, purposely die before dealing the final hit, and you are done.

The Soul Stitch item is unlocked by completing the achievement All Natural.

Surprisingly not the most frustrating achievement but definitely requires you to be very familiar with moving around to avoid triggering enemy attacks.

The method I used was equipping the inverted candle, requires unlocking the Diamond Spoon.

For stats I made sure to have enough strength to one or two shot most things early on. I generally tried to pump clarity first and defense second. I generally let my special effects and spell books take care of high defense enemies. The purple poison spell book is best for that.

Ignore speed. The starting item for inverted candle literally guarantees that you will always go first, with low speed.

Here's a list of items to look for early.

Soul stealer - godly for rerolls

Wading rags - Intimidate for poisons is worth keeping forever. An enemy with just 3 poison does 6 damage and will kill you. Venom Guard is a close second.

Heat Shield - null early exploders.

Misting Vessel - clarity and safe movement.

Anti-pierce items are huge. Even -1 will save your life.

Doll heads can accidentally sabotage you. They increase the enemy count but it seems like the extra enemies can be stronger ones.

Entangle stops movement but and keeps enemies from doing full damage. Entangled enemies only deal piercing damage to you, so in entangle spell book and one anti-pierce item make you feel like a 5 HP tank.

For the general tips I will say the most important thing is to take time and check your movement before you do it. Clearing out chasers is first priority.

Do not be afraid to jump to the next floor or skip the bonus rooms. Even if you haven't gained anything from the current floor.

Something to keep in mind is that if you quit to the main menu then continue, you will start the floor over. Randomness is mostly seeded (predetermined), so if you do the exact same thing every time you get the exact same result.

Loading twice on one floor will spawn a passive but deadly wall. Sometimes this can be helpful since it can block chasing enemies on your left side, so doing this on purpose can be a good idea.

For stat points, get enough attack to one shot most things. Anytime you have the chance try to increase your clarity. Having a bunch of souls to reroll for ideal items in mid-game is very important.

At the start you basically want to clear the first few floors and see what kind of loot you get, resetting if it's not helpful. Ambush rooms are ideal since they can drop blues and purples as early as floor 2. Wishing wells too, to stack your stats early, throw the spoon in ASAP.

Building up a good stash of +HP commons is important. Things like the glass shield will help you survive early and also give you enough health to equip any -HP items for more build flexibility.

I stopped raising my health at about 20 to 30 points. Perhaps 5-10 health was from stat points and the rest from equipment. This should give you plenty of room to make a decent build.

By floor 10 you should plan ahead and swap out +HP commons and blues for -HP purples and golds. With high clarity you should be able to access more cursed stat boosts and get more -HP and have no issue.