Lethal Exploit is a common Instant card from Kamigawa: Neon Dynasty (NEO), collector number 107. Current market price: $0.16 (foil $0.15), TCGplayer market prices via Scryfall.
Target creature gets -2/-2 until end of turn. It gets an additional -1/-1 until end of turn for each modified creature you controlled as you cast this spell. (Equipment, Auras you control, and counters are modifications.)