I have done it.

I have it. It's possible. You just have to look that you don't have something between 0.5 and 1 HP, which doesn't show.

I did it. It was certain death for both of us, but the 10 energy revival fee (after which I gave my teammate much more than 1/2 pip) was worth the achievement.

According to the wiki, each bar you see fall off of you correlates to 1/4 of a bar in your health meter. This would indicate that health is done in increments of .25 and that you'd need either 1.0 or 1.25 health in order to give your partner .5. Because if you have 1.5, you'll give him .75.

It may have been updated to be more precise (ie, 1.7's and all), but I think if they had made that change, some trigger happy editor would have updated the wiki as well.

My advice is to go into a tier 1 with a friend and just watch jellies take a bar away at a time. That way you can keep track of exactly how much you have.

done it too but you just gotta have the right health...1 bar (just kidding) but seriously it can be done

already did it. Just go beat JK with some friends, with whatever health you have left, go have a friend suicide into the bomb blocks there. Revive them until it works out. Go heal to offset some minor changes.

You have to do this when your bar says 1 hp. And remember, 1 hp may not be 1 hp so you've gotta keep trying until it is. The game rounds up bars so that case where you revived them with 1.5 hp, it "looked" like 1 bar each but you really split each other into 0.75 hp. Which is also why you can't revive anyone with that type of health.

Or perhaps you could do this in the Advanced Training Hall as well.

If in doubt, just observe when your HP bars are divisible by powers of 2 (like 8 or 16 HP), and have full health. Eventually the whole act of reviving a continuously-dying person from a full-health bar will halve yoru HP in even intervals, till you have exactly 1HP bar left, and where the achievement is assured.

"Please note that the health display may show a full bar of health, when it fact, it is only 3/4 full. If this is the case, a knight will not be able to revive a fellow knight using this method."

taken from here http://wiki.spiralknights.com/Reviving

^there you go thats the explanation behind this achievement being harder than it shoul ^^

Can they please replace all this bar nonsense with hard numbers?

I like the bars, part of the whole visual presentation.

But like the option to turn on damage, the option to have numbers would be nice.

I did it before and never did it again.

(1) The number of dropped bars on being hit per actual health lost varies from tier to tier (4 at T1, 2 at T2, 1 at T3).
(2) Health is NOT discretized to quarters; it's continuous(-ish), but rounded up to the nearest half. (So if you revive someone when you have 1.5 apparent health, you have somewhere in (1, 1.5] health before, and somewhere in (0.5, 0.75] health after.)
(3) Most relevantly to the achievement: The game prevents you from getting one-shotted, and the way it does so is by dropping you to 1 HP if you have "significantly" more than 1 HP (not sure exactly how much you need; it might even depend on the attack that hits you) but would take damage that exceeds your current health total. This is easy to see in T3; get hit several times by the same attack, and you'll see something like 5.5, 5.5, 3 (drop to 1) damage. The thing is, when you get dropped to 1 HP in this manner, you have exactly the right amount to revive someone for the achievement. Incidentally, this is a great (if risky) way to make the most out of your health in T3 (in lower tiers, the damage amounts aren't quite high enough for the savings to be noticeable); if you're fairly confident you won't get hit multiple times in a row, allow yourself to drop to 1 HP before grabbing hearts or using a potion in the middle of combat, and then only grab enough to allow the "no 1-shot" rule to trigger again. (Oh, but don't do this against enemies that can shock or burn you, for obvious reasons.)

I got it the day achievements were released.