Assassinated Assassin

Painborn (Each 1 life you pay while casting this
pays for {1}. It enters the battlefield with a -1/-1 counter on it for each 1 life paid this way,)
When Assassinated Assassin enters the battlefield, target creature gets -X/-X until end
of turn where X is equal to the number of -1/-1 counters on Assassinated Assassin.
"It's mostly 'cos of him that we're referred to as a 'ragtag bunch'." -- Lorius of the Revellers