Heartbreaker

This achievement can be a little tricky as a 120 because you can easily do too much damage and kill the boss too early.

Take off all of your gear. If your abilities require a weapon, use a low-level one.

Auto attack the boss down to 75% to trigger the heart phase. Damage transfers from the heart to the boss, so try keep his health as close to 75% as possible. If he's too much lower at the beginning of the heart phase, he'll die before the heart does and you'll fail.

Once the heart is out, damage it quickly. You need to kill it on the first heart phase or else his health will be too low to finish the achievement in subsequent heart phases phases triggered at 50% and 25% boss health.

Once the heart is dead, he'll return to full health and you can kill him normally and get the achievement.

Just got the achievement with 70 lvl warrior.

At first, [item=97919] works perfectly. Checked combat log to find out exactly 100 times damage reduction or 1% if you like. I've tried it on some trash around 40k health. My completely naked warrior did 3130 per hit while initial damage was 313'000.

Then waited for 30m for shrinker cooldown to fade and started punching the guy. He had 750k as 100% so it's not a big deal to calculate that damage rate was very easy to handle, like two/three hits for a percent or smth like that. When at 75% the heart appeared, it died on its own (that thing surprised me, but I decided to continue). Then I've equipped all the gear after cancelling the shrinker buff and stopping attack and then closed the case.

Good luck to everyone!

EDIT: it's completely achievable at 80 lvl! Just done all the same with DH. Had 39'600 per hit naked with shrinker (or 82'700 crit). Reached 74% in no time, killed heart in two punches and so on.

EDIT: if you're out of shrinker and have no idea how to get it, check the comment by Kaelith here [item=97919]

I went into this thinking you could just use foam sword to do a single soft swing but it turns out that you can't use it in a raid instance. You can however use the [item=97919] to get a nice damage debuff and it will last for 3 mins which is more than enough time.

I did still remove my weapon and equip some grey trash that I picked up inside the raid because my bare fist just wasn't pulling enough damage to get him to 75% fast enough..