Bart, Holistic Assassin

Whenever Bart attacks, put a victim counter on
target creature an opponent controls.
Whenever a creature with a victim counter on it
dies, put a +1/+1 counter on Bart.
If Bart would take noncombat damage from a
source an opponent controls, flip a coin. If you
win the flip, prevent that damage and Bart deals
that much damage to any target.