Potent Betrayal

Gain control of target creature you don't control. Put a +1/+1 counter on it and untap it. It gains haste and has "{t}: This creature deals damage equal to its power to its owner" Sacrifice it at the end of turn.
"On this plane, the ones you trust the most are often the most likely to stab you in the back for even the smallest promise of power" - Jira, Fury