Cruel Sadist is a rare Creature — Human Assassin card from Magic 2015 (M15), collector number 93. Current market price: $0.26 (foil $0.79), TCGplayer market prices via Scryfall.
{B}, {T}, Pay 1 life: Put a +1/+1 counter on this creature. {2}{B}, {T}, Remove X +1/+1 counters from this creature: It deals X damage to target creature.