Cruel Sadist — ruling 1

You can remove any +1/+1 counters from Cruel Sadist to activate its second ability, not just those put on Cruel Sadist by its first ability.

Cruel Sadist : règles, fonctionnement et interactions (MTG)

Cruel Sadist is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

, , Pay 1 life: Put a +1/+1 counter on this creature. , , Remove X +1/+1 counters from this creature: It deals X damage to target creature.

How it works : Cruel Sadist

Original English text — Wizards of the Coast / Scryfall

#1July 18, 2014· Wizards of the Coast
You can remove any +1/+1 counters from Cruel Sadist to activate its second ability, not just those put on Cruel Sadist by its first ability.
No other card is named in this ruling.