Alecto, Ringleader

Menace, Deathtouch
When Alecto, Ringleader enters the battlefield, destroy target tapped creature with mana value 3 or less.

Other assassins you control get +1/+1
and menace.
When Alecto becomes blocked by one or more creatures, put a -1/-1 counter on each of them.
If a creature you do not control with a -1/-1 counter would be put into a graveyard instead exile it.