If your life total is brought to 0 or less at the same time that creatures you control are dealt lethal damage, you lose the game before Vindictive Vampire’s triggered ability goes on the stack.

In a Two-Headed Giant game, Vindictive Vampire’s ability causes the opposing team to lose 2 life and you gain 1 life.

If Vindictive Vampire dies at the same time as one or more other creatures you control, Vindictive Vampire’s ability triggers for each of those other creatures.