Ability: Heart Breaker

The user will stand completely still for about three seconds, and then pierce his/hers weapon right through the targeted enemy's heart. This attack has a great chance of critting. If the caster is hit before the strike is ready, the attack will be cancelled, and you will not be able to unleash the attack within 30 seconds (to Mars), and before you're back in Stealth.
You don't have to be behind your oppoment.

Advanced Stealth skill, only useable by rogues, or rangers who also specialize in the art of Stealth.
Can only be used in Stealth, and while wielding a dagger, a knife or a shortsword.

I think this is a great ability!
Just have some questions about it?
Is it a one hit kill attack! Like a KO attack, does it kill instantly at the first try if succeded? And if so shouldnt there then be a lvl limit on it so you probably just cant kill like a lvl 10 hero!
Cause it is named Heart Breaker, so that simply means that you break the target units heart, which he would probably die of no matter what!?

If the attack is to only deal a great amount of damage but not quit kill the target unit! Then it could be perfect for either Dota Maps or maybe an Angel Arena?

But anyways, long story short!
Great ability

I've considered your suggestion, Dark Angel, and I think that it SHOULD be a One-hit-one-kill skill. Except if the targeted enemy is a hero above level six, then it will only damage 75% of the units (targeted unit) full life. If the enemy hero is above level eight the attack will only deal 60% dmg of the hero enemy's full life.