Decimater Beetle would help add to the numbers on negative counters you produce by letting you move them from your creatures to your opponents'. Too many Hapatras, runs the possibility of hand stalls.
Soulstinger will accumulate negative counters and let you slam an opponenr's creature as well.
Decimator of the Provinces is your finisher, but I hesitate at its high cost. You should be able to swarm a weakened opponent from tokens by the time he would hit the field.