Nero, the Corrupter

Nero, the Corrupter has Protection from
creatures with curse counters.
{b/g}{t}: Place a curse counter on target creature.
{3}{b/g}{b/g} Remove a curse counter: Target creature
gains trample and gets +X/+0 until end of turn,
where X is its power. At the beginning of the
next end step, destroy that creature if it
attacked this turn.
"Power always comes at a price."