Blood Lust 
Instant
If target creature has toughness 5 or greater, it gets +4/-4 until end of turn. Otherwise, it gets +4/-X until end of turn, where X is its toughness minus 1.
Legality
standardNOT LEGALpioneerNOT LEGALmodernNOT LEGALlegacyLEGALvintageLEGALcommanderLEGAL