How does the ability of Bloodthirsty Aerialist resolve with other life link creatures?
The scenario unfolds as follows:


You declare bloodthirsty Aerialist and Blood Burglar as attackers.
Your opponent declares blockers for these creatures.
All damage is dealt. At the same time, Blood Burglar's lifelink causes you to gain 2 life.
Bloodthirsty Aerialist's ability is triggered and goes on the stack (but doesn't resolve yet).
State based actions are checked. If either of these creatures have enough damage on them to die, they are put into the graveyard.
Bloodthirsty Aerialist's ability resolves (assuming players pass priority). If Bloodthirsty Aerialist is not on the battlefield, the ability does nothing. If the creature is on the battlefield, it gets a single +1/+1 counter.


Bloodthirsty Aerialist will only deal 2 damage to the creature that blocks it, and if it is dealt three damage, the +1/+1 counter won't be placed on it in time to save it from dying.