Jack Bauer, CTU Agent

When Jack enters, create a legendary artifact token
Nuclear Bomb with "This enters with 5 charge counters.
Whenever it has either zero or ten charge counters,
sacrifice it. When it leaves the battlefield, all creatures get
-X/-X where X is the number of charge counters on it.
On your upkeep, add 1 charge counter to it."

{t}: Sacrifice target creature. Remove up to X counters from target artifact where X is the sacrificed creature's power.

{u/b}: Regenerate.