Doomslayer

Doomslayer enters the battlefield with 1 BFG artifact.
Sacrifice BFG, destroy target creature. Use this
only as an instant. When Doomslayer enters
the battlefield, choose target player.
All target opponents creatures must fight
DoomSlayer 1 by 1, regardless of their abilities.
For Each creature Doomslayer defeats, it gets
+2/+2. If there are no
creatures left to fight. Doomslayer deals lethal
damage to target player.